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Sample records for metal cluster deposition

  1. Surface deposition and encapsulation of metallic clusters

    NASA Astrophysics Data System (ADS)

    Hund, Jared Franklin

    In this work metallic clusters are produced by both encapsulation in an aerogel matrix and deposition on a surface. Entrapment of metal clusters inside aerogels is accomplished though synthesis of a hydrogel precursor, washing it with an aqueous metal salt solution, and controlled reduction of the metal. Although the aerogel matrix stabilizes and prevents subsequent loss or aggregation of the clusters once they are produced, controlling the rate of reduction is key to the size and morphology of the clusters. In order to do this, both radiolytic and chemical reduction methods are used. The radiolytic technique for the formation of metal cluster aerogel composites utilizes gamma radiation to reduce the solution of Ag+ or [AuCl 4]- ions inside of the hydrogel precursor. After exposure to gamma rays, the previously colorless gels have the coloration typical of colloids of Au (pink) and Ag (yellow/brown) clusters. Typical gamma doses are between 2 to 3.5 kGy for hydrogels containing 10-4 to 10-3 mol·L-1 metal solutions. Subsequent characterization confirmed the presence of metal clusters with a fcc structure. The cluster diameters varied between 10 and 200nm, depending on the synthesis parameters. More conventional chemical reduction is also employed in this work to produce noble metal clusters in an aerogel matrix. Hydrogels were washed in a basic solution of Ag+ or [AuCl4]- ions, and formaldehyde was added to the solution. The reduction proceeded relatively slowly, allowing the formaldehyde to diffuse into the hydrogel before complete reduction took place. This procedure was also used to produce alloys of gold and silver clusters embedded in silica aerogels. Also included in this dissertation is the surface deposition of metallic clusters on a silicon surface. The apparatus built produces a cold beam of gas droplets that pick up evaporated metal clusters and deposit them on a surface. The gas clusters are produced by supersonic expansion of a gas (Ar, He, or N2

  2. The structure of deposited metal clusters generated by laser evaporation

    NASA Astrophysics Data System (ADS)

    Faust, P.; Brandstättner, M.; Ding, A.

    1991-09-01

    Metal clusters have been produced using a laser evaporation source. A Nd-YAG laser beam focused onto a solid silver rod was used to evaporate the material, which was then cooled to form clusters with the help of a pulsed high pressure He beam. TOF mass spectra of these clusters reveal a strong occurrence of small and medium sized clusters ( n<100). Clusters were also deposited onto grid supported thin layers of carbon-films which were investigated by transmission electron microscopy. Very high resolution pictures of these grids were used to analyze the size distribution and the structure of the deposited clusters. The diffraction pattern caused by crystalline structure of the clusters reveals 3-and 5-fold symmetries as well as fcc bulk structure. This can be explained in terms of icosahedron and cuboctahedron type clusters deposited on the surface of the carbon layer. There is strong evidence that part of these cluster geometries had already been formed before the depostion process. The non-linear dependence of the cluster size and the cluster density on the generating conditions is discussed. Therefore the samples were observed in HREM in the stable DEEKO 100 microscope of the Fritz-Haber-Institut operating at 100 KV with the spherical aberration c S =0.5 mm. The quality of the pictures was improved by using the conditions of minimum phase contrast hollow cone illumination. This procedure led to a minimum of phase contrast artefacts. Among the well-crystallized particles were a great amount of five- and three-fold symmetries, icosahedra and cuboctahedra respectively. The largest clusters with five- and three-fold symmetries have been found with diameters of 7 nm; the smallest particles displaying the same undistorted symmetries were of about 2 mm. Even smaller ones with strong distortions could be observed although their classification is difficult. The quality of the images was improved by applying Fourier filtering techniques.

  3. Simulation studies of electroless metal deposition using gold nano-clusters on polymeric surfaces

    NASA Astrophysics Data System (ADS)

    Lively, Mike; Bhattacharya, Aniket; Grabill, Chris; Kuebler, Stephen M.; Dutta, Aniruddha; Heinrich, Helge

    2010-03-01

    We report lattice Monte Carlo (MC) simulation studies of deposition of metallic silver on randomly distributed gold nano clusters on a polymeric surface. The gold nano-clusters act as seeds for further deposition of silver atoms. We assume ballistic growth for the growth of metallic silver on gold clusters but treat the lateral growth (which eventually form bridges among original clusters) with different rules and study the evolving morphologies of the deposited silver atoms as a function of the surface density and the size distribution of gold nano-clusters and compare simulation results with those obtained from TEM studies of the prepared samples.

  4. Improved metal cluster deposition on a genetically engineered tobacco mosaic virus template

    NASA Astrophysics Data System (ADS)

    Lee, Sang-Yup; Royston, Elizabeth; Culver, James N.; Harris, Michael T.

    2005-07-01

    Improved depositions of various metal clusters onto a biomolecular template were achieved using a genetically engineered tobacco mosaic virus (TMV). Wild-type TMV was genetically altered to display multiple solid metal binding sites through the insertion of two cysteine residues within the amino-terminus of the virus coat protein. Gold, silver, and palladium clusters synthesized through in situ chemical reductions could be readily deposited onto the genetically modified template via the exposed cysteine-derived thiol groups. Metal cluster coatings on the cysteine-modified template were more densely deposited and stable than similar coatings on the unmodified wild-type template. Combined, these results confirm that the introduction of cysteine residues onto the outer surface of the TMV coat protein enhances the usefulness of this virus as a biotemplate for the deposition of metal clusters.

  5. Selective electrodesorption based atomic layer deposition (SEBALD): a novel electrochemical route to deposit metal clusters on Ag(111).

    PubMed

    Innocenti, M; Bellandi, S; Lastraioli, E; Loglio, F; Foresti, M L

    2011-09-20

    The possibility of synergic effects of some metals on the catalytic activity of silver led us to study the way to perform controlled deposition on silver. In fact, many metals of technological interest such as Co, Ni, and Fe cannot be deposited at underpotential on silver, and any attempt to control the deposition at overpotential, even at potentials slightly negative of the Nernst value, did not allow an effective control. However, due to the favorable energy gain involved in the formation of the corresponding sulfides, these metals can be deposited at underpotential on sulfur covered silver. The deposition is surface limited and the successive electrodesorption of sulfur leaves confined clusters of metals. The method can also be used to obtain metal clusters of different size. In fact, the alternate underpotential deposition of elements that form a compound is the basis of the electrochemical atomic layer epitaxy (ECALE), and the reiteration of the basic cycle allows us to obtain sulfide deposits whose thickness increases with the number of cycles. Therefore, the successive selective desorption of sulfur leaves increasing amounts of metals.

  6. Ionized cluster beam deposition and epitaxy of metal films on large lattice misfit substrates

    NASA Astrophysics Data System (ADS)

    Yamada, Isao

    1991-01-01

    This paper reviews the metal film formation by the ionized cluster beam (ICB) technique on various kinds of substrates. The ICB enables heteroepitaxy of metal films for lattice misfit larger than 25 percent. The film growth process was studied by in situ MEED, AES and XPS analyses. The films were also examined by ex situ electron diffraction and atomic resolution TEM. On Si(111), single crystal Al film was formed. The Al deposited on Si(100) formed a bicrystal structure. The film-substrate interface and the bicrystal grain boundary were very sharp and had little distortion of atomic arrangement. This explains the high thermal stability of the metal films deposited by ICB. Epitaxial Al films were also formed on CaF2, Ge, GaAs, and sapphire substrates.

  7. Model studies in catalysis with uhv-deposited metal particles and clusters

    NASA Technical Reports Server (NTRS)

    Poppa, H.

    1984-01-01

    Small supported metal particles have become a popular area of intense research interest, and important contributions to the considered problems are being made from the fields of uhv technology, thin film physics surface science, and surface and thin film instrumentation. Attention is given to insulating supports, particulate metal deposits and their properties, metal/support interactions and gas exposures, and integrated experimental approaches. It is concluded that major contributions to the field of model catalysis should be forthcoming in the near future from uhv-based methods of research. Catalysis and catalysis-related problem areas expected to benefit from advanced model studies include catalyst preparation processing, sintering mechanisms for metals and alloys, separation of initial and final state effects for supported clusters, and the influence of particle and/or support morphologies.

  8. Ionized cluster beam deposition

    NASA Technical Reports Server (NTRS)

    Kirkpatrick, A. R.

    1983-01-01

    Ionized Cluster Beam (ICB) deposition, a new technique originated by Takagi of Kyoto University in Japan, offers a number of unique capabilities for thin film metallization as well as for deposition of active semiconductor materials. ICB allows average energy per deposited atom to be controlled and involves impact kinetics which result in high diffusion energies of atoms on the growth surface. To a greater degree than in other techniques, ICB involves quantitative process parameters which can be utilized to strongly control the characteristics of films being deposited. In the ICB deposition process, material to be deposited is vaporized into a vacuum chamber from a confinement crucible at high temperature. Crucible nozzle configuration and operating temperature are such that emerging vapor undergoes supercondensation following adiabatic expansion through the nozzle.

  9. Improvements in Ionized Cluster-Beam Deposition

    NASA Technical Reports Server (NTRS)

    Fitzgerald, D. J.; Compton, L. E.; Pawlik, E. V.

    1986-01-01

    Lower temperatures result in higher purity and fewer equipment problems. In cluster-beam deposition, clusters of atoms formed by adiabatic expansion nozzle and with proper nozzle design, expanding vapor cools sufficiently to become supersaturated and form clusters of material deposited. Clusters are ionized and accelerated in electric field and then impacted on substrate where films form. Improved cluster-beam technique useful for deposition of refractory metals.

  10. Tribological coatings for complex mechanical elements produced by supersonic cluster beam deposition of metal dichalcogenide nanoparticles

    NASA Astrophysics Data System (ADS)

    Piazzoni, C.; Buttery, M.; Hampson, M. R.; Roberts, E. W.; Ducati, C.; Lenardi, C.; Cavaliere, F.; Piseri, P.; Milani, P.

    2015-07-01

    Fullerene-like MoS2 and WS2 nanoparticles can be used as building blocks for the fabrication of fluid and solid lubricants. Metal dichalcogenide films have a very low friction coefficient in vacuum, therefore they have mostly been used as solid lubricants in space and vacuum applications. Unfortunately, their use is significantly hampered by the fact that in the presence of humidity, oxygen and moisture, the low-friction properties of these materials rapidly degrade due to oxidation. The use of closed-cage MoS2 and WS2 nanoparticles may eliminate this problem, although the fabrication of lubricant thin films starting from dichalcogenide nanoparticles is, to date, a difficult task. Here we demonstrate the use of supersonic cluster beam deposition for the coating of complex mechanical elements (angular contact ball bearings) with nanostructured MoS2 and WS2 thin films. We report structural and tribological characterization of the coatings in view of the optimization of tribological performances for aerospace applications.

  11. High rate deposition system for metal-cluster/SiO x C y H z -polymer nanocomposite thin films

    NASA Astrophysics Data System (ADS)

    Peter, T.; Rehders, S.; Schürmann, U.; Strunskus, T.; Zaporojtchenko, V.; Faupel, F.

    2013-06-01

    A system for deposition of nanocomposite materials consisting of a SiO x C y H z -polymer matrix and Ag nanoclusters is presented. Ag nanoclusters with sizes between 2 and 20 nm are produced in a gas aggregation cluster source and are deposited through a focused beam at a high rate. This cluster source is presented in detail and the characteristics of the produced nanoclusters are shown. Simultaneously, a SiO x C y H z -polymer matrix is grown from the precursor hexamethyldisiloxane in an RF plasma. The beam of clusters is deposited into the growing polymer, forming the composite material. This process allows the rapid deposition of composite material with varying metal nanocluster concentrations and properties. Since the cluster generation is separated from the matrix growth, the properties of both can be controlled independently. In this study, we present two types of nanocomposite samples, in the first the Ag nanoclusters are homogeneously distributed in the matrix, in the second type the Ag nanoclusters form a layer which is covered by the matrix. These samples are investigated using transmission electron micrography to determine the morphology. Furthermore, the optical properties are probed using optical transmission spectroscopy and the plasmonic resonance behavior is discussed.

  12. Selective deposition of Pt onto supported metal clusters for fuel cell electrocatalysts

    NASA Astrophysics Data System (ADS)

    Jeon, Tae-Yeol; Pinna, Nicola; Yoo, Sung Jong; Ahn, Docheon; Choi, Sun Hee; Willinger, Marc-Georg; Cho, Yong-Hun; Lee, Kug-Seung; Park, Hee-Young; Yu, Seung-Ho; Sung, Yung-Eun

    2012-09-01

    We report a new method for deposition of Pt on a metal core to develop real electrocatalysts with significantly reduced amounts of expensive Pt as well as enhanced activity for oxygen reduction reaction. Ru and Pd have different crystal structures and modify the electronic structure of Pt to a different extent (shifts in d-band center). They were chosen as core materials to examine whether hydroquinone dissolved in ethanol can be used to deposit additional Pt atoms onto preformed core nanoparticles, and whether the modified d-character of Pt on different host metals can result in the enhanced ORR activity. The physicochemical characteristics of Pd-Pt and Ru-Pt core-shell nanoparticles are investigated. The core-shell structure was identified through a combination of experimental methods, employing electron microscopy, electrochemical measurements, and synchrotron X-ray measurements such as powder X-ray diffraction, X-ray absorption fine structure, and X-ray photoelectron spectroscopy. The hydroquinone reduction method proved to be an excellent route for the epitaxial growth of a Pt shell on the metal cores, leading to enhanced ORR activities.We report a new method for deposition of Pt on a metal core to develop real electrocatalysts with significantly reduced amounts of expensive Pt as well as enhanced activity for oxygen reduction reaction. Ru and Pd have different crystal structures and modify the electronic structure of Pt to a different extent (shifts in d-band center). They were chosen as core materials to examine whether hydroquinone dissolved in ethanol can be used to deposit additional Pt atoms onto preformed core nanoparticles, and whether the modified d-character of Pt on different host metals can result in the enhanced ORR activity. The physicochemical characteristics of Pd-Pt and Ru-Pt core-shell nanoparticles are investigated. The core-shell structure was identified through a combination of experimental methods, employing electron microscopy

  13. Reactivity of Metal Clusters.

    PubMed

    Luo, Zhixun; Castleman, A W; Khanna, Shiv N

    2016-12-14

    We summarize here the research advances on the reactivity of metal clusters. After a simple introduction of apparatuses used for gas-phase cluster reactions, we focus on the reactivity of metal clusters with various polar and nonpolar molecules in the gas phase and illustrate how elementary reactions of metal clusters proceed one-step at a time under a combination of geometric and electronic reorganization. The topics discussed in this study include chemical adsorption, addition reaction, cleavage of chemical bonds, etching effect, spin effect, the harpoon mechanism, and the complementary active sites (CAS) mechanism, among others. Insights into the reactivity of metal clusters not only facilitate a better understanding of the fundamentals in condensed-phase chemistry but also provide a way to dissect the stability and reactivity of monolayer-protected clusters synthesized via wet chemistry.

  14. Platinum-ruthenium bimetallic clusters on graphite: a comparison of vapor deposition and electroless deposition methods.

    PubMed

    Galhenage, Randima P; Xie, Kangmin; Diao, Weijian; Tengco, John Meynard M; Seuser, Grant S; Monnier, John R; Chen, Donna A

    2015-11-14

    Bimetallic Pt-Ru clusters have been grown on highly ordered pyrolytic graphite (HOPG) surfaces by vapor deposition and by electroless deposition. These studies help to bridge the material gap between well-characterized vapor deposited clusters and electrolessly deposited clusters, which are better suited for industrial catalyst preparation. In the vapor deposition experiments, bimetallic clusters were formed by the sequential deposition of Pt on Ru or Ru on Pt. Seed clusters of the first metal were grown on HOPG surfaces that were sputtered with Ar(+) to introduce defects, which act as nucleation sites for Pt or Ru. On the unmodified HOPG surface, both Pt and Ru clusters preferentially nucleated at the step edges, whereas on the sputtered surface, clusters with relatively uniform sizes and spatial distributions were formed. Low energy ion scattering experiments showed that the surface compositions of the bimetallic clusters are Pt-rich, regardless of the order of deposition, indicating that the interdiffusion of metals within the clusters is facile at room temperature. Bimetallic clusters on sputtered HOPG were prepared by the electroless deposition of Pt on Ru seed clusters from a Pt(+2) solution using dimethylamine borane as the reducing agent at pH 11 and 40 °C. After exposure to the electroless deposition bath, Pt was selectively deposited on Ru, as demonstrated by the detection of Pt on the surface by XPS, and the increase in the average cluster height without an increase in the number of clusters, indicating that Pt atoms are incorporated into the Ru seed clusters. Electroless deposition of Ru on Pt seed clusters was also achieved, but it should be noted that this deposition method is extremely sensitive to the presence of other metal ions in solution that have a higher reduction potential than the metal ion targeted for deposition.

  15. The effect of metal cluster deposition route on structure and photocatalytic activity of mono- and bimetallic nanoparticles supported on TiO2 by radiolytic method

    NASA Astrophysics Data System (ADS)

    Klein, Marek; Nadolna, Joanna; Gołąbiewska, Anna; Mazierski, Paweł; Klimczuk, Tomasz; Remita, Hynd; Zaleska-Medynska, Adriana

    2016-08-01

    TiO2 (P25) was modified with small and relatively monodisperse mono- and bimetallic clusters (Ag, Pd, Pt, Ag/Pd, Ag/Pt and Pd/Pt) induced by radiolysis to improve its photocatalytic activity. The as-prepared samples were characterized by X-ray fluorescence spectrometry (XRF), photoluminescence spectrometry (PL), diffuse reflectance spectroscopy (DRS), X-ray powder diffractometry (XRD), scanning transition electron microscopy (STEM) and BET surface area analysis. The effect of metal type (mono- and bimetallic modification) as well as deposition method (simultaneous or subsequent deposition of two metals) on the photocatalytic activity in toluene removal in gas phase under UV-vis irradiation (light-emitting diodes- LEDs) and phenol degradation in liquid phase under visible light irradiation (λ > 420 nm) were investigated. The highest photoactivity under Vis light was observed for TiO2 co-loaded with platinum (0.1%) and palladium (0.1%) clusters. Simultaneous addition of metal precursors results in formation of larger metal nanoparticles (15-30 nm) on TiO2 surface and enhances the Vis-induced activity of Ag/Pd-TiO2 up to four times, while the subsequent metal ions addition results in formation of metal particle size ranging from 4 to 20 nm. Subsequent addition of metal precursors results in formation of BNPs (bimetallic nanoparticle) composites showing higher stability in four cycles of toluene degradation under UV-vis. Obtained results indicated that direct electron transfer from the BNPs to the conduction band of the semiconductor is responsible for visible light photoactivity, whereas superoxide radicals (such as O2rad- and rad OOH) are responsible for pollutants degradation over metal-TiO2 composites.

  16. Alkali Metal Cluster Theory.

    NASA Astrophysics Data System (ADS)

    Chen, Jian

    Available from UMI in association with The British Library. Requires signed TDF. In this thesis, we apply the tight-binding Hubbard model to alkali metal clusters with Hartree-Fock self-consistent methods and perturbation methods for the numerical calculations. We have studied the relation between the equilibrium structures and the range of the hopping matrix elements in the Hubbard Hamiltonian. The results show that the structures are not sensitive to the interaction range but are determined by the number of valence electrons each atom has. Inertia tensors are used to analyse the symmetries of the clusters. The principal axes of the clusters are determined and they are the axes of rotational symmetries of clusters if the clusters have any. The eigenvalues of inertia tensors which are the indication of the deformation of clusters are compared between our model and the ellipsoidal jellium model. The agreement is good for large clusters. At a finite temperature, the thermal motion fluctuates the structures. We defined a fluctuation function with the distance matrix of a cluster. The fluctuation has been studied with the Monte-Carlo simulation method. Our studies show that the clusters remain in the solid state when temperature is low. The small values of fluctuation functions indicates the thermal vibration of atoms around their equilibrium positions. If the temperature is high, the atoms are delocalized. The cluster melts and enters the liquid region. The cluster melting is simulated by the Monte-Carlo simulation with the fluctuation function we defined. Energy levels of clusters are calculated from the Hubbard model. Ionization potentials and magic numbers are also obtained from these energy levels. The results confirm that the Hubbard model is a good approximation for a small cluster. The excitation energy is presented by the difference between the original level and excited level, and the electron-hole interactions. We also have studied cooling of clusters

  17. Photobiomolecular deposition of metallic particles and films

    DOEpatents

    Hu, Zhong-Cheng

    2005-02-08

    The method of the invention is based on the unique electron-carrying function of a photocatalytic unit such as the photosynthesis system I (PSI) reaction center of the protein-chlorophyll complex isolated from chloroplasts. The method employs a photo-biomolecular metal deposition technique for precisely controlled nucleation and growth of metallic clusters/particles, e.g., platinum, palladium, and their alloys, etc., as well as for thin-film formation above the surface of a solid substrate. The photochemically mediated technique offers numerous advantages over traditional deposition methods including quantitative atom deposition control, high energy efficiency, and mild operating condition requirements.

  18. Catalysis applications of size-selected cluster deposition

    SciTech Connect

    Vajda, Stefan; White, Michael G.

    2015-10-23

    In this Perspective, we review recent studies of size-selected cluster deposition for catalysis applications performed at the U.S. DOE National Laboratories, with emphasis on work at Argonne National Laboratory (ANL) and Brookhaven National Laboratory (BNL). The focus is on the preparation of model supported catalysts in which the number of atoms in the deposited clusters is precisely controlled using a combination of gas-phase cluster ion sources, mass spectrometry, and soft-landing techniques. This approach is particularly effective for investigations of small nanoclusters, 0.5-2 nm (<200 atoms), where the rapid evolution of the atomic and electronic structure makes it essential to have precise control over cluster size. Cluster deposition allows for independent control of cluster size, coverage, and stoichiometry (e.g., the metal-to-oxygen ratio in an oxide cluster) and can be used to deposit on any substrate without constraints of nucleation and growth. Examples are presented for metal, metal oxide, and metal sulfide cluster deposition on a variety of supports (metals, oxides, carbon/diamond) where the reactivity, cluster-support electronic interactions, and cluster stability and morphology are investigated. Both UHV and in situ/operando studies are presented that also make use of surface-sensitive X-ray characterization tools from synchrotron radiation facilities. Novel applications of cluster deposition to electrochemistry and batteries are also presented. This review also highlights the application of modern ab initio electronic structure calculations (density functional theory), which can essentially model the exact experimental system used in the laboratory (i.e., cluster and support) to provide insight on atomic and electronic structure, reaction energetics, and mechanisms. As amply demonstrated in this review, the powerful combination of atomically precise cluster deposition and theory is able to address fundamental aspects of size-effects, cluster

  19. Catalysis applications of size-selected cluster deposition

    DOE PAGES

    Vajda, Stefan; White, Michael G.

    2015-10-23

    In this Perspective, we review recent studies of size-selected cluster deposition for catalysis applications performed at the U.S. DOE National Laboratories, with emphasis on work at Argonne National Laboratory (ANL) and Brookhaven National Laboratory (BNL). The focus is on the preparation of model supported catalysts in which the number of atoms in the deposited clusters is precisely controlled using a combination of gas-phase cluster ion sources, mass spectrometry, and soft-landing techniques. This approach is particularly effective for investigations of small nanoclusters, 0.5-2 nm (<200 atoms), where the rapid evolution of the atomic and electronic structure makes it essential to havemore » precise control over cluster size. Cluster deposition allows for independent control of cluster size, coverage, and stoichiometry (e.g., the metal-to-oxygen ratio in an oxide cluster) and can be used to deposit on any substrate without constraints of nucleation and growth. Examples are presented for metal, metal oxide, and metal sulfide cluster deposition on a variety of supports (metals, oxides, carbon/diamond) where the reactivity, cluster-support electronic interactions, and cluster stability and morphology are investigated. Both UHV and in situ/operando studies are presented that also make use of surface-sensitive X-ray characterization tools from synchrotron radiation facilities. Novel applications of cluster deposition to electrochemistry and batteries are also presented. This review also highlights the application of modern ab initio electronic structure calculations (density functional theory), which can essentially model the exact experimental system used in the laboratory (i.e., cluster and support) to provide insight on atomic and electronic structure, reaction energetics, and mechanisms. As amply demonstrated in this review, the powerful combination of atomically precise cluster deposition and theory is able to address fundamental aspects of size

  20. Catalysis applications of size-selected cluster deposition.

    SciTech Connect

    Vajda, Stefan; White, Michael G.

    2015-12-01

    In this Perspective, we review recent studies of size-selected cluster deposition for catalysis applications performed at the U.S. DOE National Laboratories, with emphasis on work at Argonne National Laboratory (ANL) and Brookhaven National Laboratory (BNL). The focus is on the preparation of model supported catalysts in which the number of atoms in the deposited clusters is precisely controlled using a combination of gas-phase cluster ion sources, mass spectrometry, and soft-landing techniques. This approach is particularly effective for investigations of small nanoclusters, 0.5-2 nm (<200 atoms), where the rapid evolution of the atomic and electronic structure makes it essential to have precise control over cluster size. Cluster deposition allows for independent control of cluster size, coverage, and stoichiometry (e.g., the metal-to-oxygen ratio in an oxide cluster) and can be used to deposit on any substrate without constraints of nucleation and growth. Examples are presented for metal, metal oxide, and metal sulfide cluster deposition on a variety of supports (metals, oxides, carbon/diamond) where the reactivity, cluster-support electronic interactions, and cluster stability and morphology are investigated. Both UHV and in situ/operando studies are presented that also make use of surface-sensitive X-ray characterization tools from synchrotron radiation facilities. Novel applications of cluster deposition to electrochemistry and batteries are also presented. This review also highlights the application of modern ab initio electronic structure calculations (density functional theory), which can essentially model the exact experimental system used in the laboratory (i.e., cluster and support) to provide insight on atomic and electronic structure, reaction energetics, and mechanisms. As amply demonstrated in this review, the powerful combination of atomically precise cluster deposition and theory is able to address fundamental aspects of size-effects, cluster

  1. Design and capabilities of an experimental setup based on magnetron sputtering for formation and deposition of size-selected metal clusters on ultra-clean surfaces

    NASA Astrophysics Data System (ADS)

    Hartmann, H.; Popok, V. N.; Barke, I.; von Oeynhausen, V.; Meiwes-Broer, K.-H.

    2012-07-01

    The design and performance of an experimental setup utilizing a magnetron sputtering source for production of beams of ionized size-selected clusters for deposition in ultra-high vacuum is described. For the case of copper cluster formation the influence of different source parameters is studied and analyzed. Size-selected clusters are deposited on substrates and the efficiency of an electrostatic quadrupole mass selector is tested. Height analysis using atomic force microscopy (AFM) demonstrates relative standard size deviations of 7%-10% for the particles of various sizes between 6 nm and 19 nm. Combined analysis by AFM and transmission electron microscopy reveals that the clusters preserve almost spherical shape after the deposition on amorphous carbon substrates. Supported nanoparticles of a few nanometres in diameter have crystalline structure with a face-centered cubic (fcc) lattice.

  2. Design and capabilities of an experimental setup based on magnetron sputtering for formation and deposition of size-selected metal clusters on ultra-clean surfaces.

    PubMed

    Hartmann, H; Popok, V N; Barke, I; von Oeynhausen, V; Meiwes-Broer, K-H

    2012-07-01

    The design and performance of an experimental setup utilizing a magnetron sputtering source for production of beams of ionized size-selected clusters for deposition in ultra-high vacuum is described. For the case of copper cluster formation the influence of different source parameters is studied and analyzed. Size-selected clusters are deposited on substrates and the efficiency of an electrostatic quadrupole mass selector is tested. Height analysis using atomic force microscopy (AFM) demonstrates relative standard size deviations of 7%-10% for the particles of various sizes between 6 nm and 19 nm. Combined analysis by AFM and transmission electron microscopy reveals that the clusters preserve almost spherical shape after the deposition on amorphous carbon substrates. Supported nanoparticles of a few nanometres in diameter have crystalline structure with a face-centered cubic (fcc) lattice.

  3. Sputter Deposition of Metallic Sponges

    SciTech Connect

    Jankowski, A F; Hayes, J P

    2002-01-18

    Metallic films are grown with a sponge-like morphology in the as-deposited condition using planar magnetron sputtering. The morphology of the deposit is characterized by metallic continuity in three dimensions with continuous porosity on the sub-micron scale. The stabilization of the metallic sponge is directly correlated with a limited range for the sputter deposition parameters of working gas pressure and substrate temperature. This sponge-like morphology augments the features as generally understood in the classic zone models of growth for physical vapor deposits. Nickel coatings are deposited with working gas pressures up to 4 Pa and for substrate temperatures up to 1100 K. The morphology of the deposits is examined in plan and in cross-section with scanning electron microscopy. The parametric range of gas pressure and substrate temperature (relative to absolute melt point) for the deposition processing under which the metallic sponges are produced appear universal for many metals, as for example, including gold, silver, and aluminum.

  4. Two photon photoemission of deposited silver clusters

    NASA Astrophysics Data System (ADS)

    Busolt, U.; Cottancin, E.; Röhr, H.; Socaciu, L.; Leisner, T.; Wöste, L.

    We use time resolved two photon photoemission to study the stability of size selected silver clusters deposited onto highly oriented pyrolytic graphite (HOPG) substrates. Size-selected Agn+ clusters (n=2-9) are deposited at low coverage onto HOPG surfaces at liquid nitrogen temperatures. After deposition, the samples are irradiated by a series of ultrashort laser pulse pairs. Photoelectrons created by two photon photoemission are collected in a magnetic bottle type time-of-flight photoelectron spectrometer. Their kinetic energy distribution is recorded as a function of the delay time between subsequent light pulses. With the exception of Ag3 the size dependence of the photoelectron spectra reveals a pronounced odd/even effect, which is well known for gas phase silver clusters. This indicates that the deposited clusters retain their size and identity on the sample. The lifetime of the photoexcitation rises with cluster size. This is attributed to an increasing electronic density of states for larger clusters.

  5. Photoionization of oxidized metal clusters

    SciTech Connect

    Dao, P.D.; Peterson, K.I.; Castleman, A.W. Jr.

    1984-01-01

    Oxidized metal clusters (Na/sub x/O and K/sub x/O for 2< or =x< or =4) were formed in a gas phase reaction between metal clusters and an oxidizing gas using a double expansion technique. Their appearance potentials were measured using a molecular beam-photoionization mass spectrometer system. These first photoionization data for oxidized clusters provide information on trends of ionization potentials as a function of the degree of aggregation. The ionization potentials do not differ greatly from the analogous metallic species, but in the case of the sodium tetramer the value does fall below that of the bare metal cluster. This finding is in accord with what has been observed as an influence of impurities on the work function of the bulk sodium. The results are also of interest concerning questions of octet rule violations and hypervalency.

  6. Metal deposition using seed layers

    DOEpatents

    Feng, Hsein-Ping; Chen, Gang; Bo, Yu; Ren, Zhifeng; Chen, Shuo; Poudel, Bed

    2013-11-12

    Methods of forming a conductive metal layers on substrates are disclosed which employ a seed layer to enhance bonding, especially to smooth, low-roughness or hydrophobic substrates. In one aspect of the invention, the seed layer can be formed by applying nanoparticles onto a surface of the substrate; and the metallization is achieved by electroplating an electrically conducting metal onto the seed layer, whereby the nanoparticles serve as nucleation sites for metal deposition. In another approach, the seed layer can be formed by a self-assembling linker material, such as a sulfur-containing silane material.

  7. Palladium clusters deposited on the heterogeneous substrates

    NASA Astrophysics Data System (ADS)

    Wang, Kun; Liu, Juanfang; Chen, Qinghua

    2016-07-01

    To improve the performance of the Pd composite membrane prepared by the cold spraying technology, it is extremely essential to give insights into the deposition process of the cluster and the heterogeneous deposition of the big Pd cluster at the different incident velocities on the atomic level. The deposition behavior, morphologies, energetic and interfacial configuration were examined by the molecular dynamic simulation and characterized by the cluster flattening ratio, the substrate maximum local temperature, the atom-embedded layer number and the surface-alloy formation. According to the morphology evolution, three deposition stages and the corresponding structural and energy evolution were clearly identified. The cluster deformation and penetrating depth increased with the enhancement of the incident velocity, but the increase degree also depended on the substrate hardness. The interfacial interaction between the cluster and the substrate can be improved by the higher substrate local temperature. Furthermore, it is found that the surface alloys were formed by exchanging sites between the cluster and substrate atoms, and the cluster atoms rearranged following as the substrate lattice arrangement from bottom to up in the deposition course. The ability and scope of the structural reconstruction are largely determined by both the size and incident energy of the impacted cluster.

  8. Metal monolayer deposition by replacement of metal adlayers on electrode surfaces

    NASA Astrophysics Data System (ADS)

    Brankovic, S. R.; Wang, J. X.; Adžić, R. R.

    2001-03-01

    A new metal deposition method is demonstrated by deposition of a submonolayer of Pt, a monolayer of Pd and a bilayer of Ag on Au(1 1 1) surfaces by using a Cu adlayer as a template. The deposition of these metals occurs as a spontaneous irreversible redox process in which a Cu adlayer, obtained by underpotential deposition, is oxidized by more noble metal cations, which are reduced and simultaneously deposited. The Pt deposit is a two-dimensional submonolayer consisting of partially interconnected nano-clusters of monoatomic height. Pd forms a uniform, but textured monolayer, while Ag forms a bilayer. The deposit of each metal uniformly covers the entire gold surface without preferential deposition along the step edges. This method provides surface adlayer-controlled growth, as compared to the current distribution controlled growth in conventional electrodeposition.

  9. Internal gettering by metal alloy clusters

    DOEpatents

    Buonassisi, Anthony; Heuer, Matthias; Istratov, Andrei A.; Pickett, Matthew D.; Marcus, Mathew A.; Weber, Eicke R.

    2010-07-27

    The present invention relates to the internal gettering of impurities in semiconductors by metal alloy clusters. In particular, intermetallic clusters are formed within silicon, such clusters containing two or more transition metal species. Such clusters have melting temperatures below that of the host material and are shown to be particularly effective in gettering impurities within the silicon and collecting them into isolated, less harmful locations. Novel compositions for some of the metal alloy clusters are also described.

  10. Metallic bonding and cluster structure

    SciTech Connect

    Soler, Jose M.; Beltran, Marcela R.; Michaelian, Karo; Garzon, Ignacio L.; Ordejon, Pablo; Sanchez-Portal, Daniel

    2000-02-15

    Knowledge of the structure of clusters is essential to predict many of their physical and chemical properties. Using a many-body semiempirical Gupta potential (to perform global minimizations), and first-principles density functional calculations (to confirm the energy ordering of the local minima), we have recently found [Phys. Rev. Lett. 81, 1600 (1998)] that there are many intermediate-size disordered gold nanoclusters with energy near or below the lowest-energy ordered structure. This is especially surprising because we studied ''magic'' cluster sizes, for which very compact-ordered structures exist. Here, we show how the analysis of the local stress can be used to understand the physical origin of this amorphization. We find that the compact ordered structures, which are very stable for pair potentials, are destabilized by the tendency of metallic bonds to contract at the surface, because of the decreased coordination. The amorphization is also favored by the relatively low energy associated to bondlength and coordination disorder in metals. Although these are very general properties of metallic bonding, we find that they are especially important in the case of gold, and we predict some general trends in the tendency of metallic clusters towards amorphous structures. (c) 2000 The American Physical Society.

  11. Molecular dynamics simulation of gold cluster growth during sputter deposition

    NASA Astrophysics Data System (ADS)

    Abraham, J. W.; Strunskus, T.; Faupel, F.; Bonitz, M.

    2016-05-01

    We present a molecular dynamics simulation scheme that we apply to study the time evolution of the self-organized growth process of metal cluster assemblies formed by sputter-deposited gold atoms on a planar surface. The simulation model incorporates the characteristics of the plasma-assisted deposition process and allows for an investigation over a wide range of deposition parameters. It is used to obtain data for the cluster properties which can directly be compared with recently published experimental data for gold on polystyrene [M. Schwartzkopf et al., ACS Appl. Mater. Interfaces 7, 13547 (2015)]. While good agreement is found between the two, the simulations additionally provide valuable time-dependent real-space data of the surface morphology, some of whose details are hidden in the reciprocal-space scattering images that were used for the experimental analysis.

  12. Molecular dynamics simulation of gold cluster growth during sputter deposition

    SciTech Connect

    Abraham, J. W. Bonitz, M.; Strunskus, T.; Faupel, F.

    2016-05-14

    We present a molecular dynamics simulation scheme that we apply to study the time evolution of the self-organized growth process of metal cluster assemblies formed by sputter-deposited gold atoms on a planar surface. The simulation model incorporates the characteristics of the plasma-assisted deposition process and allows for an investigation over a wide range of deposition parameters. It is used to obtain data for the cluster properties which can directly be compared with recently published experimental data for gold on polystyrene [M. Schwartzkopf et al., ACS Appl. Mater. Interfaces 7, 13547 (2015)]. While good agreement is found between the two, the simulations additionally provide valuable time-dependent real-space data of the surface morphology, some of whose details are hidden in the reciprocal-space scattering images that were used for the experimental analysis.

  13. Structure stability and spectroscopy of metal clusters

    SciTech Connect

    Not Available

    1993-01-01

    Theory based on self-consistent field-linear combinations of atomic orbitals-molecular orbital theory was applied to clusters. Four areas were covered: electronic structure, equilibrium geometries, and stability of charged clusters, interaction of metal clusters with H and halogen atoms, thermal stability of isolated clusters, and stability and optical properties of hetero-atomic clusters. (DLC)

  14. Semiconductor assisted metal deposition for nanolithography applications

    DOEpatents

    Rajh, Tijana; Meshkov, Natalia; Nedelijkovic, Jovan M.; Skubal, Laura R.; Tiede, David M.; Thurnauer, Marion

    2002-01-01

    An article of manufacture and method of forming nanoparticle sized material components. A semiconductor oxide substrate includes nanoparticles of semiconductor oxide. A modifier is deposited onto the nanoparticles, and a source of metal ions are deposited in association with the semiconductor and the modifier, the modifier enabling electronic hole scavenging and chelation of the metal ions. The metal ions and modifier are illuminated to cause reduction of the metal ions to metal onto the semiconductor nanoparticles.

  15. Semiconductor assisted metal deposition for nanolithography applications

    DOEpatents

    Rajh, Tijana; Meshkov, Natalia; Nedelijkovic, Jovan M.; Skubal, Laura R.; Tiede, David M.; Thurnauer, Marion

    2001-01-01

    An article of manufacture and method of forming nanoparticle sized material components. A semiconductor oxide substrate includes nanoparticles of semiconductor oxide. A modifier is deposited onto the nanoparticles, and a source of metal ions are deposited in association with the semiconductor and the modifier, the modifier enabling electronic hole scavenging and chelation of the metal ions. The metal ions and modifier are illuminated to cause reduction of the metal ions to metal onto the semiconductor nanoparticles.

  16. Ammonia release method for depositing metal oxides

    DOEpatents

    Silver, G.L.; Martin, F.S.

    1994-12-13

    A method is described for depositing metal oxides on substrates which is indifferent to the electrochemical properties of the substrates and which comprises forming ammine complexes containing metal ions and thereafter effecting removal of ammonia from the ammine complexes so as to permit slow precipitation and deposition of metal oxide on the substrates. 1 figure.

  17. Ammonia release method for depositing metal oxides

    DOEpatents

    Silver, Gary L.; Martin, Frank S.

    1994-12-13

    A method of depositing metal oxides on substrates which is indifferent to the electrochemical properties of the substrates and which comprises forming ammine complexes containing metal ions and thereafter effecting removal of ammonia from the ammine complexes so as to permit slow precipitation and deposition of metal oxide on the substrates.

  18. Surface Finish after Laser Metal Deposition

    NASA Astrophysics Data System (ADS)

    Rombouts, M.; Maes, G.; Hendrix, W.; Delarbre, E.; Motmans, F.

    Laser metal deposition (LMD) is an additive manufacturing technology for the fabrication of metal parts through layerwise deposition and laser induced melting of metal powder. The poor surface finish presents a major limitation in LMD. This study focuses on the effects of surface inclination angle and strategies to improve the surface finish of LMD components. A substantial improvement in surface quality of both the side and top surfaces has been obtained by laser remelting after powder deposition.

  19. Production of metal particles and clusters

    NASA Technical Reports Server (NTRS)

    Mcmanus, S. P.

    1982-01-01

    The feasibility of producing novel metals or metal clusters in a low gravity environment was studied. The production of coordinately unsaturated metal carbonyls by thermolysis or photolysis of stable metal carbonyls has the potential to generate novel catalysts by this technique. Laser irradiation of available metal carbonyls was investigated. It is found that laser induced decomposition of metal carbonyls is feasible for producing a variety of coordinately unsaturated species. Formation of clustered species does occur but is hampered by weak metal-metal bonds.

  20. Apparatus for gas-metal arc deposition

    DOEpatents

    Buhrmaster, Carol L.; Clark, Denis E.; Smartt, Herschel B.

    1991-01-01

    Apparatus for gas-metal arc deposition of metal, metal alloys, and metal matrix composites. The apparatus contains an arc chamber for confining a D.C. electrical arc discharge, the arc chamber containing an outlet orifice in fluid communication with a deposition chamber having a deposition opening in alignment with the orifice for depositing metal droplets on a coatable substrate. Metal wire is passed continuously into the arc chamber in alignment with the orifice. Electric arcing between the metal wire anode and the orifice cathode produces droplets of molten metal from the wire which pass through the orifice and into the deposition chamber for coating a substrate exposed at the deposition opening. When producing metal matrix composites, a suspenion of particulates in an inert gas enters the deposition chamber via a plurality of feed openings below and around the orifice so that reinforcing particulates join the metal droplets to produce a uniform mixture which then coats the exposed substrate with a uniform metal matrix composite.

  1. Method for gas-metal arc deposition

    DOEpatents

    Buhrmaster, C.L.; Clark, D.E.; Smartt, H.B.

    1990-11-13

    Method and apparatus for gas-metal arc deposition of metal, metal alloys, and metal matrix composites are disclosed. The apparatus contains an arc chamber for confining a D.C. electrical arc discharge, the arc chamber containing an outlet orifice in fluid communication with a deposition chamber having a deposition opening in alignment with the orifice for depositing metal droplets on a coatable substrate. Metal wire is passed continuously into the arc chamber in alignment with the orifice. Electric arcing between the metal wire anode and the orifice cathode produces droplets of molten metal from the wire which pass through the orifice and into the deposition chamber for coating a substrate exposed at the deposition opening. When producing metal matrix composites, a suspension of particulates in an inert gas enters the deposition chamber via a plurality of feed openings below and around the orifice so that reinforcing particulates join the metal droplets to produce a uniform mixture which then coats the exposed substrate with a uniform metal matrix composite. 1 fig.

  2. Method for gas-metal arc deposition

    DOEpatents

    Buhrmaster, Carol L.; Clark, Denis E.; Smartt, Herschel B.

    1990-01-01

    Method and apparatus for gas-metal arc deposition of metal, metal alloys, and metal matrix composites. The apparatus contains an arc chamber for confining a D.C. electrical arc discharge, the arc chamber containing an outlet orifice in fluid communication with a deposition chamber having a deposition opening in alignment wiht the orifice for depositing metal droplets on a coatable substrate. Metal wire is passed continuously into the arc chamber in alignment with the orifice. Electric arcing between the metal wire anode and the orifice cathode produces droplets of molten metal from the wire which pass through the orifice and into the deposition chamber for coating a substrate exposed at the deposition opening. When producing metal matrix composites, a suspension of particulates in an inert gas enters the deposition chamber via a plurality of feed openings below and around the orifice so that reinforcing particulates join the metal droplets to produce a uniform mixture which then coats the exposed substrate with a uniform metal matrix composite.

  3. Reactive cluster model of metallic glasses

    SciTech Connect

    Jones, Travis E.; Miorelli, Jonathan; Eberhart, Mark E.

    2014-02-28

    Though discovered more than a half century ago metallic glasses remain a scientific enigma. Unlike crystalline metals, characterized by short, medium, and long-range order, in metallic glasses short and medium-range order persist, though long-range order is absent. This fact has prompted research to develop structural descriptions of metallic glasses. Among these are cluster-based models that attribute amorphous structure to the existence of clusters that are incommensurate with crystalline periodicity. Not addressed, however, are the chemical factors stabilizing these clusters and promoting their interconnections. We have found that glass formers are characterized by a rich cluster chemistry that above the glass transformation temperature promotes exchange as well as static and vibronic sharing of atoms between clusters. The vibronic mechanism induces correlated motions between neighboring clusters and we hypothesize that the distance over which these motions are correlated mediates metallic glass stability and influences critical cooling rates.

  4. Quantum chemical treatments of metal clusters.

    PubMed

    Weigend, Florian; Ahlrichs, Reinhart

    2010-03-28

    This work focuses on finding and rationalizing the building principles of clusters with approximately 300 atoms of different types of metals: main group elements (Al, Sn), alkaline earth metals (Mg), transition metals (Pd) and clusters consisting of two different elements (Ir and Pt). Two tools are inevitable for this purpose: (i) quantum chemical methods that are able to treat a given cluster with both sufficient accuracy and efficiency and (ii) algorithms that are able to systematically scan the (3n-6)-dimensional potential surface of an n-atomic cluster for promising isomers. Currently, the only quantum chemical method that can be applied to metal clusters is density functional theory (DFT). Other methods either do not account for the multi-reference character of metal clusters or are too expensive and thus can be applied only to clusters of very few atoms, which usually is not sufficient for studying the building principles. The accuracy of DFT is not known a priori, but extrapolations to bulk values from calculated series of data show satisfying agreement with experimental data. For scans of the potential surface, simulated annealing techniques or genetic algorithms were used for the smaller clusters (approx. 20-30 atoms), and for the larger clusters considerations were restricted to selected packings and shapes. For the mixed-metallic clusters, perturbation theory turned out to be efficient and successful for finding the most promising distributions of the two atom types at the different sites.

  5. A new nanomaterial synthesized from size-selected, ligand-free metal clusters

    NASA Astrophysics Data System (ADS)

    Li, X.; Wepasnick, K.; Tang, X.; Fairbrother, D. H.; Bowen, K. H.; Dollinger, A.; Strobel, C. H.; Huber, J.; Mangler, T.; Luo, Y.; Proch, S.; Gantefoer, G.

    2014-03-01

    Thins films are synthesized by deposition of size-selected Mon- cluster anions on an inert substrate. Scanning tunneling microscopy pictures indicate that the deposited material consists of individual particles with diameters corresponding to the size of the preformed clusters from the gas phase. Previous attempts to manufacture cluster materials from metals failed since these clusters coalesced at room temperature. Our data suggest the possibility to synthesize new nanomaterials from clusters of high fusing metals. This may prove to be the key to harness size-dependent and tuneable properties of clusters for creating novel classes of functional tailor-made materials.

  6. Metal clusters and nanoparticles in dielectric matrices: Formation and optical properties

    NASA Astrophysics Data System (ADS)

    Gladskikh, I. A.; Vartanyan, T. A.

    2016-12-01

    The optical properties of thin dielectric films with metal inclusions and their dependence on thermal and laser annealing are studied experimentally. Metal clusters (Ag, Au, and Cu) in dielectric materials (Al2O3 and SiO2) are obtained by simultaneous vacuum deposition of metal and dielectric on the surface of a corresponding dielectric substrate (sapphire and quartz). It is shown that, depending on the deposited dielectric material, on the weight ratio of deposited metal and dielectric, and on the subsequent thermal treatment, one can obtain different metal structures, from clusters with a small number of atoms to complex dendritic plasmonic structures.

  7. Titanium-dioxide film formation using gas cluster ion beam assisted deposition technique

    NASA Astrophysics Data System (ADS)

    Nakatsu, O.; Matsuo, J.; Omoto, K.; Seki, T.; Takaoka, G.; Yamada, I.

    2003-05-01

    Gas cluster ion beam (GCIB) assisted deposition technique has been applied to form titanium-dioxide films. When oxygen cluster ions collide on solid surfaces, oxygen molecules in the clusters enhance oxidation due to high density energy deposition. Metal titanium pellets were used as source material for EB evaporation, because evaporation with metal pellets is much stable than that of oxide pellets. Films were deposited on sapphire (0 0 0 1) substrates with various conditions. Characteristics of the films were examined by use of XRD, RBS and AFM. When film was deposited with the acceleration voltage of 7 kV at 473 K, the well c-oriented rutile TiO 2 film was formed with average roughness of 0.4 nm. Without assistance of GCIB rough amorphous film was formed in an atmosphere of oxygen. Very smooth surface films with good crystallinity were formed by GCIB assisted deposition technique.

  8. Highly bactericidal Ag nanoparticle films obtained by cluster beam deposition.

    PubMed

    Cavaliere, Emanuele; De Cesari, Sebastiano; Landini, Giulia; Riccobono, Eleonora; Pallecchi, Lucia; Rossolini, Gian Maria; Gavioli, Luca

    2015-08-01

    The recent emergence of bacterial pathogens resistant to most or all available antibiotics is among the major global public health problems. As indirect transmission through contaminated surfaces is a main route of dissemination for most of such pathogens, the implementation of effective antimicrobial surfaces has been advocated as a promising approach for their containment, especially in the hospital settings. However, traditional wet synthesis methods of nanoparticle-based antimicrobial materials leave a number of key points open for metal surfaces: such as adhesion to the surface and nanoparticle coalescence. Here we demonstrate an alternative route, i.e. supersonic cluster beam deposition, to obtain antimicrobial Ag nanoparticle films deposited directly on surfaces. The synthesized films are simple to produce with controlled density and thickness, are stable over time, and are shown to be highly bactericidal against major Gram positive and Gram negative bacterial pathogens, including extensively drug-resistant strains. The use of silver nanoparticle in health care is getting more widespread. The authors here describe the technique of cluster beam deposition for spraying silver on surfaces used in health care sectors. This may open a new avenue for future anti-bacterial coatings. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.

  9. Mechanical Instability of Oxidized Metal Clusters

    NASA Astrophysics Data System (ADS)

    Celino, Massimo; Cleri, Fabrizio; D'Agostino, Gregorio; Rosato, Vittorio

    1996-09-01

    A mechanism to explain the complete oxidation of small metal clusters is proposed, based on the occurrence of a mechanical instability driven by the expansion of the progressively oxidized cluster surface and the subsequent stress relaxation. Molecular dynamics simulations of spherical Pd clusters show that an expanded surface layer is capable of straining the inner core of the cluster up to the point of inducing cavitation. These findings allow the interpretation of recent experimental results in which oxidized Pd clusters exhibit a hollow spherical shape.

  10. A Simple MO Treatment of Metal Clusters.

    ERIC Educational Resources Information Center

    Sahyun, M. R. V.

    1980-01-01

    Illustrates how a qualitative description of the geometry and electronic characteristics of homogeneous metal clusters can be obtained using semiempirical MO (molecular orbital theory) methods. Computer applications of MO methods to inorganic systems are also described. (CS)

  11. Strategic metal deposits of the Arctic Zone

    NASA Astrophysics Data System (ADS)

    Bortnikov, N. S.; Lobanov, K. V.; Volkov, A. V.; Galyamov, A. L.; Vikent'ev, I. V.; Tarasov, N. N.; Distler, V. V.; Lalomov, A. V.; Aristov, V. V.; Murashov, K. Yu.; Chizhova, I. A.; Chefranov, R. M.

    2015-11-01

    Mineral commodities rank high in the economies of Arctic countries, and the status of mineral resources and the dynamics of their development are of great importance. The growing tendency to develop strategic metal resources in the Circumarctic Zone is outlined in a global perspective. The Russian Arctic Zone is the leading purveyor of these metals to domestic and foreign markets. The comparative analysis of tendencies in development of strategic metal resources of the Arctic Zone in Russia and other countries is crucial for the elaboration of trends of geological exploration and research engineering. This paper provides insight into the development of Arctic strategic metal resources in global perspective. It is shown that the mineral resource potential of the Arctic circumpolar metallogenic belt is primarily controlled by large and unique deposits of nonferrous, noble, and rare metals. The prospective types of economic strategic metal deposits in the Russian Arctic Zone are shown.

  12. Uniform deposition of size-selected clusters using Lissajous scanning

    SciTech Connect

    Beniya, Atsushi; Watanabe, Yoshihide; Hirata, Hirohito

    2016-05-15

    Size-selected clusters can be deposited on the surface using size-selected cluster ion beams. However, because of the cross-sectional intensity distribution of the ion beam, it is difficult to define the coverage of the deposited clusters. The aggregation probability of the cluster depends on coverage, whereas cluster size on the surface depends on the position, despite the size-selected clusters are deposited. It is crucial, therefore, to deposit clusters uniformly on the surface. In this study, size-selected clusters were deposited uniformly on surfaces by scanning the cluster ions in the form of Lissajous pattern. Two sets of deflector electrodes set in orthogonal directions were placed in front of the sample surface. Triangular waves were applied to the electrodes with an irrational frequency ratio to ensure that the ion trajectory filled the sample surface. The advantages of this method are simplicity and low cost of setup compared with raster scanning method. The authors further investigated CO adsorption on size-selected Pt{sub n} (n = 7, 15, 20) clusters uniformly deposited on the Al{sub 2}O{sub 3}/NiAl(110) surface and demonstrated the importance of uniform deposition.

  13. DEPOSITION OF METAL ON NONMETAL FILAMENT

    DOEpatents

    Magel, T.T.

    1959-02-10

    A method is described for purifying metallic uranium by passing a halogen vapor continuously over the impure uranium to form uranium halide vapor and immediately passing the halide vapor into contact with a nonmetallic refractory surface which is at a temperature above the melting point of uranium metal. The halide is decomposed at the heated surface depositing molten metal, which collects and falls into a receiver below.

  14. Studies of silicon cluster--metal atom compound formation in a supersonic molecular beam

    SciTech Connect

    Beck, S.M.

    1987-10-01

    The first observation of a reaction between a metal atom and silicon in a supersonic jet to form metal atom silicon clusters is reported. Using the technique of laser vaporization supersonic expansion with metal carbonyl seeded carrier gas, clusters of the form MSi/sub n/ have been detected by ArF and KrF laser photoionization time-of-flight mass spectrometry. Three transition metals have been investigated, Cr, Mo, and W. The dominant product cluster peaks observed in the mass spectra obtained for all three metals corresponds to identical but remarkable cluster stoichiometries. The dominant peaks have formulas given by MSi/sub n/ where n = 15 and n = 16. The metal--semiconductor clusters are relatively more stable towards photofragmentation than the bare silicon cluster of the same size. The observation of these new species may be relevant to reactions which occur at the interface between a silicon wafer and deposited metals.

  15. The magic numbers of metal and metal alloy clusters

    SciTech Connect

    Yamada, Y.; Castleman, A.W. Jr. )

    1992-09-15

    Pure metal and metal alloy clusters including Cu{sub {ital n}}, Ag{sub {ital n}}, Cu{sub {ital n}}Ag{sub {ital m}}, Cu{sub {ital n}}Al{sub {ital m}}, Cu{sub {ital n}}In{sub {ital m}}, Ag{sub {ital n}}Al{sub {ital m}}, Ag{sub {ital n}}In{sub {ital m}}, and Cu{sub {ital n}}Pb{sub {ital m}} are produced by a gas aggregation source and investigated by time-of-flight mass spectrometry following ionization with a KrF excimer laser. In the case of pure metal clusters (Cu{sub {ital n}},Ag{sub {ital n}},In{sub {ital n}}), as well as alloy clusters composed of these metals, magic numbers are observed in their cluster ions which correspond to jellium shell closings (counting the total valence electrons from the component metals). These findings are in good agreement with their expected free-electron behavior. Interestingly, the abundance of pure Pb{sub {ital n}}{sup +} corresponds to species which are expected to be especially stable due to their geometric structure. A similar situation also arises for the Pb-rich alloy clusters. By contrast, the metal alloy clusters Cu{sub {ital n}}Pb{sub {ital m}}{sup +} show magic numbers at jellium shell closing in the series of Cu-rich clusters.

  16. Young star cluster evolution and metallicity .

    NASA Astrophysics Data System (ADS)

    Mapelli, M.; Bressan, A.

    Young star clusters (SCs) are the cradle of stars and the site of important dynamical processes. We present N-body simulations of young SCs including recipes for metal-dependent stellar evolution and mass loss by stellar winds. We show that metallicity affects significantly the collapse and post-core collapse phase, provided that the core collapse timescale is of the same order of magnitude as the lifetime of massive stars. In particular, the reversal of core collapse is faster for metal-rich SCs, where stellar winds are stronger. As a consequence, the half-mass radius of metal-poor SCs expands more than that of metal-rich SCs.

  17. ENERGY DEPOSITION PROFILES AND ENTROPY IN GALAXY CLUSTERS

    SciTech Connect

    Chaudhuri, Anya; Majumdar, Subhabrata; Nath, Biman B. E-mail: subha@tifr.res.in

    2012-11-10

    We report the results of our study of fractional entropy enhancement in the intracluster medium (ICM) of the clusters from the representative XMM-Newton cluster structure survey. We compare the observed entropy profile of these clusters with that expected for the ICM without any feedback, as well as with the introduction of preheating and cooling. We make the first estimate of the total, as well as radial, non-gravitational energy deposition up to r {sub 500} for this large, nearly flux-limited, sample of clusters. We find that the total energy deposition corresponding to the entropy enhancement is proportional to the cluster temperature (and hence cluster mass). The energy deposition per particle scaled by T {sub sp}, {Delta}E/T {sub sp} has a similar profile in all clusters, and is more pronounced in the central regions. Our results support models of entropy enhancement through active galactic nucleus feedback.

  18. Chemical vapor deposition of group IIIB metals

    DOEpatents

    Erbil, Ahmet

    1989-01-01

    Coatings of Group IIIB metals and compounds thereof are formed by chemical vapor deposition, in which a heat decomposable organometallic compound of the formula (I) ##STR1## where M is a Group IIIB metal, such as lanthanum or yttrium and R is a lower alkyl or alkenyl radical containing from 2 to about 6 carbon atoms, with a heated substrate which is above the decomposition temperature of the organometallic compound. The pure metal is obtained when the compound of the formula I is the sole heat decomposable compound present and deposition is carried out under nonoxidizing conditions. Intermetallic compounds such as lanthanum telluride can be deposited from a lanthanum compound of formula I and a heat decomposable tellurium compound under nonoxidizing conditions.

  19. Chemical vapor deposition of group IIIB metals

    DOEpatents

    Erbil, A.

    1989-11-21

    Coatings of Group IIIB metals and compounds thereof are formed by chemical vapor deposition, in which a heat decomposable organometallic compound of the formula given in the patent where M is a Group IIIB metal, such as lanthanum or yttrium and R is a lower alkyl or alkenyl radical containing from 2 to about 6 carbon atoms, with a heated substrate which is above the decomposition temperature of the organometallic compound. The pure metal is obtained when the compound of the formula 1 is the sole heat decomposable compound present and deposition is carried out under nonoxidizing conditions. Intermetallic compounds such as lanthanum telluride can be deposited from a lanthanum compound of formula 1 and a heat decomposable tellurium compound under nonoxidizing conditions.

  20. Size to density coupling of supported metallic clusters.

    PubMed

    Gross, Elad; Asscher, Micha

    2009-01-28

    One of the difficulties in standard growth of metallic nano-clusters on oxide substrates as model catalysts is the strong coupling between clusters size and density. Employing multiple cycles, amorphous solid water-buffer layer assisted growth (ASW-BLAG) procedure, we demonstrate how the size to density coupling can be eliminated under certain conditions. In this study, gold clusters were deposited on a SiO2/Si(100) substrate in UHV, using ASW as a buffer layer assisting aggregation and growth. The clusters were imaged ex situ by tapping mode atomic force microscope (AFM) and high-resolution scanning electron microscope (HR-SEM). In situ Auger electron spectroscopy (AES) measurements have led to independent evaluation of the gold covered area. In order to increase the clusters density we have introduced a multiple BLAG procedure, in which, a BALG cycle is repeated up to 10 times. The cluster density can be increased this way by more than five fold without changing their size. Above a specific number of cycles, however, the cluster density reaches saturation and a gradual increase in clusters size is observed. Larger clusters correlate with lower saturation density following multiple BLAG cycles. This observation is explained in terms of long range cluster-cluster attraction between clusters already on the substrate and those approaching in the next BLAG cycle. This attraction is more pronounced as the clusters become larger. We have shown that at saturation density, inter-cluster distance can not be smaller than 20 nm for clusters 4 nm in diameter or larger. Employing two consecutive BLAG cycles, characterized by different parameters (metal dosage and buffer layer thickness) result in a bi-modal size distribution. Moreover, it is demonstrated that one can prepare this way co-adsorbed bi-metallic film of e.g. Au and Pd clusters, with specific density and size on the same substrate. The ASW-BLAG procedure is thus expected to introduce a new pathway for tailor made

  1. The effects of deposition methods for metal catalyst formation in carbon nanotubes growth

    NASA Astrophysics Data System (ADS)

    Isa, Siti S. Mat; Ramli, Muhammad M.

    2014-10-01

    In this study, we examine the effect of two different metal catalyst deposition methods in carbon nanotubes (CNT) growth for interconnect application. Metal support layer, which is Titanium Nitride (TiN) was first deposited on Silicon Dioxide (SiO2) pads, Then, nickel (Ni) catalyst was deposited, first; by sputtering technique to form uniform thin film, and second; by cluster tool where spherical metal catalyst was formed. These metal catalysts were annealed at 400 °C, 500 °C and 600 °C. The image shows that the number of Ni particles for cluster techniques was higher than thin film sample. While, the average diameter of particles for thin film samples were higher than that in cluster samples. For the CNT growth, the density of the growth was believed to be higher for thin film samples than cluster samples. Raman spectroscopy was used to investigate the quality of CNT.

  2. APPARATUS FOR VACUUM DEPOSITION OF METALS

    DOEpatents

    Milleron, N.

    1962-03-13

    An apparatus and a method are described for continuous vacuum deposition of metals for metallic coatings, for ultra-high vacuum work, for purification of metals, for maintaining high-density electron currents, and for other uses. The apparatus comprises an externally cooled feeder tube extending into a container and adapted to feed metal wire or strip so that it emerges in a generally vertical position therein. The tube also provides shielding from the heat produced by an electron beam therein focused to impinge from a vertical direction upon the tip of the emerging wire. By proper control of the wire feed, coolant feed, and electron beam intensity, a molten ball of metal forms upon the emerging tip and remains self-supported thereon by the interaction of various forces. The metal is vaporized and travels in a line of sight direction, while additional wire is fed from the tube, so that the size of the molten ball remains constant. In the preferred embodiments, the wire is selected from a number of gettering metals and is degassed by electrical resistance in an adjacent chamber which is also partially evacuated. The wire is then fed through the feed tube into the electron beam and vaporizes and adsorbs gases to provide pumping action while being continuously deposited upon surfaces within the chamber. Ion pump electrodes may also be provided within line of sight of the vaporizing metal source to enhance the pumping action. (AEC)

  3. Structural evolution and metallicity of lead clusters

    NASA Astrophysics Data System (ADS)

    Götz, Daniel A.; Shayeghi, Armin; Johnston, Roy L.; Schwerdtfeger, Peter; Schäfer, Rolf

    2016-05-01

    The evolution of the metallic state in lead clusters and its structural implications are subject to ongoing discussions. Here we present molecular beam electric deflection studies of neutral PbN (N = 19-25, 31, 36, 54) clusters. Many of them exhibit dipole moments or anomalies of the polarizability indicating a non-metallic state. In order to resolve their structures, the configurational space is searched using the Pool Birmingham Cluster Genetic algorithm based on density functional theory. Spin-orbit effects on the geometries and dipole moments are taken into account by further relaxing them with two-component density functional theory. Geometries and dielectric properties from quantum chemical calculations are then used to simulate beam deflection profiles. Structures are assigned by the comparison of measured and simulated beam profiles. Energy gaps are calculated using time-dependent density functional theory. They are compared to Kubo gaps, which are an indicator of the metallicity in finite particles. Both, experimental and theoretical data suggest that lead clusters are not metallic up to at least 36 atoms.The evolution of the metallic state in lead clusters and its structural implications are subject to ongoing discussions. Here we present molecular beam electric deflection studies of neutral PbN (N = 19-25, 31, 36, 54) clusters. Many of them exhibit dipole moments or anomalies of the polarizability indicating a non-metallic state. In order to resolve their structures, the configurational space is searched using the Pool Birmingham Cluster Genetic algorithm based on density functional theory. Spin-orbit effects on the geometries and dipole moments are taken into account by further relaxing them with two-component density functional theory. Geometries and dielectric properties from quantum chemical calculations are then used to simulate beam deflection profiles. Structures are assigned by the comparison of measured and simulated beam profiles. Energy gaps

  4. Supersonic Bare Metal Cluster Beams. Final Report

    DOE R&D Accomplishments Database

    Smalley, R. E.

    1997-10-14

    A major portion of the project involved elucidating the relation between reactivity and the electronic structure of transition-metal (TM) clusters of 2--200 atoms, which required the construction and continuous development of two principal apparati; the Fourier Transform-Ion Cyclotron Resonance (FT-ICR) apparatus, and Ultraviolet Photoelectron Spectroscopy (UPS). Together, these machines have enabled the most detailed probing of the structure and chemical reactivity of TM clusters. Clusters of all the transition metals were included in these studies. Fundamental aspects in chemisorption, reactivity, and heterogeneous catalysis have also become better understood as a result of these experiments for important classes of systems such as H{sub 2}, CO, and CO{sub 2} adsorbed onto clusters of many of the metals listed above. In particular, a correlation was found between reactivity of H{sub 2} with Fe, Co, and Ni clusters and differences between the cluster IP and EA. As recounted in a previous technical report, the DOE`s role in the initial discovery of fullerenes at Rice was central, and from the start investigations were made into metal atoms trapped in the fullerenes cage. More recently, the authors have discovered that 2--4 atoms of La, Y, or Sc can be produced by laser vaporization of composite graphite/metal-oxide disks. This work was largely motivated by the prospects of using such endohedral TM metals for their catalytic activity without the well-known difficulties of effective support media and lack of control over particle size. Thus, while it will certainly be important to discover ways to efficiently scale up production (e.g., the solar generation method explored with DOE support), the efforts have concentrated more on characterization, purification, and manipulation of doped fullerenes. For the past two years, much of the group`s effort has involved the production, purification, and characterization of carbon nanotubes.

  5. Plasma deposition of amorphous metal alloys

    DOEpatents

    Hays, A.K.

    1979-07-18

    Amorphous metal alloy coatings are plasma-deposited by dissociation of vapors of organometallic compounds and metalloid hydrides in the presence of a reducing gas, using a glow discharge. Tetracarbonylnickel, phosphine, and hydrogen constitute a typical reaction mixture of the invention, yielding a NiPC alloy.

  6. Plasma deposition of amorphous metal alloys

    DOEpatents

    Hays, Auda K.

    1986-01-01

    Amorphous metal alloy coatings are plasma-deposited by dissociation of vapors of organometallic compounds and metalloid hydrides in the presence of a reducing gas, using a glow discharge. Tetracarbonylnickel, phosphine, and hydrogen constitute a typical reaction mixture of the invention, yielding a NiPC alloy.

  7. Observation of small metal clusters on graphite surface with scanning tunneling microscopy

    NASA Astrophysics Data System (ADS)

    Shen, Jian; Zhu, Changxin; Ma, Zili; Pang, Shijin; Xue, Zengquan

    The motivation for studying the dynamic behavior and morphology of small metal clusters on solid single crystal surface is the desire to understand the physical mechanisms evolving in the initial stages of thin-film growth. In the experiments we have used a scanning tunneling microscope to study the static morphology of small Pt and Ni clusters supported on clean graphite surfaces, as well as the dynamic behaviors of small Pt clusters in an ultrahigh vacuum chamber. The metal deposition was fulfilled by controllable evaporation from ultra-pure superfine metal wires at room temperature in UHV. The STM images of small Pt and Ni clusters on graphite substrates with atomic resolution, as well as a series of STM images reveal some transformation processes of small metal clusters on the solid crystal surfaces, which provide us a better understanding on the procedure of atomic diffusion of metal clusters. All the STM images have been performed at room temperature.

  8. (Electronic structure and reactivities of transition metal clusters)

    SciTech Connect

    Not Available

    1992-01-01

    The following are reported: theoretical calculations (configuration interaction, relativistic effective core potentials, polyatomics, CASSCF); proposed theoretical studies (clusters of Cu, Ag, Au, Ni, Pt, Pd, Rh, Ir, Os, Ru; transition metal cluster ions; transition metal carbide clusters; bimetallic mixed transition metal clusters); reactivity studies on transition metal clusters (reactivity with H{sub 2}, C{sub 2}H{sub 4}, hydrocarbons; NO and CO chemisorption on surfaces). Computer facilities and codes to be used, are described. 192 refs, 13 figs.

  9. Embedded cluster metal-polymeric micro interface and process for producing the same

    DOEpatents

    Menezes, Marlon E.; Birnbaum, Howard K.; Robertson, Ian M.

    2002-01-29

    A micro interface between a polymeric layer and a metal layer includes isolated clusters of metal partially embedded in the polymeric layer. The exposed portion of the clusters is smaller than embedded portions, so that a cross section, taken parallel to the interface, of an exposed portion of an individual cluster is smaller than a cross section, taken parallel to the interface, of an embedded portion of the individual cluster. At least half, but not all of the height of a preferred spherical cluster is embedded. The metal layer is completed by a continuous layer of metal bonded to the exposed portions of the discontinuous clusters. The micro interface is formed by heating a polymeric layer to a temperature, near its glass transition temperature, sufficient to allow penetration of the layer by metal clusters, after isolated clusters have been deposited on the layer at lower temperatures. The layer is recooled after embedding, and a continuous metal layer is deposited upon the polymeric layer to bond with the discontinuous metal clusters.

  10. O2 cluster ion assisted deposition for tin doped indium oxide (ITO) films

    NASA Astrophysics Data System (ADS)

    Matsuo, Jiro; Takaoka, Gikan; Yamada, Isao

    2001-07-01

    B S TO2 Gas Cluster Ion Beam assisted deposition technique has been developed to form ultra high quality tin doped indium-oxide (UHQ-ITO) films. This deposition process uses large cluster ions which can transport thousands of atoms in a ion with very low energy per constituent atom. Interactions between cluster ions and substrate atoms occur in the near-surface region and cluster ions can deposit their energy with a high density in a very localized surface region. The energetic oxygen clusters collapsed at the surface and reacted with the metal atoms and about 10% of them were incorporated, when the kinetic energy of the cluster ion was above 5 keV. Oxidation reaction can be enhanced by energetic cluster ion bombardment which offers a new technique for ion assisted thin film formation. Very smooth, highly transparent (>80 %) and low resistivity films, were obtained by using a 7 keV oxygen cluster ion beam. In order to realize high throughput for industrial application, a Multi-beam Gas Cluster Ion Beam equipment has been newly developed.

  11. Electrochemical Deposition Of Thiolate Monolayers On Metals

    NASA Technical Reports Server (NTRS)

    Porter, Marc D.; Weissharr, Duane E.

    1995-01-01

    Electrochemical method devised for coating metal (usually, gold) surfaces with adherent thiolate monolayers. Affords greater control over location and amount of material deposited and makes it easier to control chemical composition of deposits. One important potential use for this method lies in fabrication of chemically selective thin-film resonators for microwave oscillators used to detect pollutants: monolayer formulated to bind selectively pollutant chemical species of interest, causing increase in mass of monolayer and corresponding decrease in frequency of resonance. Another important potential use lies in selective chemical derivatization for purposes of improving adhesion, lubrication, protection against corrosion, electrocatalysis, and electroanalysis.

  12. Welding, bonding, and sealing of refractory metals by vapor deposition

    NASA Technical Reports Server (NTRS)

    1967-01-01

    Plating process welds, bonds, and seals refractory metals without weakening or changing the structure of the base metals. A metal halide compound in the vapor phase is decomposed to deposit filler metal on the base metal. The resulting bond is a true metal-to-metal bond.

  13. Carbide-reinforced metal matrix composite by direct metal deposition

    NASA Astrophysics Data System (ADS)

    Novichenko, D.; Thivillon, L.; Bertrand, Ph.; Smurov, I.

    Direct metal deposition (DMD) is an automated 3D laser cladding technology with co-axial powder injection for industrial applications. The actual objective is to demonstrate the possibility to produce metal matrix composite objects in a single-step process. Powders of Fe-based alloy (16NCD13) and titanium carbide (TiC) are premixed before cladding. Volume content of the carbide-reinforced phase is varied. Relationships between the main laser cladding parameters and the geometry of the built-up objects (single track, 2D coating) are discussed. On the base of parametric study, a laser cladding process map for the deposition of individual tracks was established. Microstructure and composition of the laser-fabricated metal matrix composite objects are examined. Two different types of structures: (a) with the presence of undissolved and (b) precipitated titanium carbides are observed. Mechanism of formation of diverse precipitated titanium carbides is studied.

  14. Reinforcement of titanium by laser metal deposition

    NASA Astrophysics Data System (ADS)

    Sampedro, Jesús; Pérez, Irene; Cárcel, Bernabé; Amigó, Vicente; Sánchez, José María

    2010-09-01

    Pure commercial titanium is widely used because of its high corrosion resistance and lower cost compared with other titanium alloys, in particular when there is no high wear requirements. Nevertheless, the wear resistance is poor and surface damage occurs in areas under contact loadings. Laser melting deposition using a high power laser is a suitable technique for manufacturing precise and defect free coatings of a dissimilar material with higher wear and corrosion resistance. In this work a good understanding of laser metal deposition mechanisms allowed to obtain defect free coatings of Ti6Al4V and TiC metal matrix composite (MMC) using a flash lamp pumped Nd:YAG laser of 1 kW. A complete investigation of the process parameters is discussed and resultant wear and corrosion properties are shown. The results show the feasibility to apply the process for manufacturing, improving or repairing high added value components for a wide range of industrial sectors.

  15. Magnetic properties of free metal clusters

    NASA Astrophysics Data System (ADS)

    Jiang, Wei

    In this dissertation, results of Stern-Gerlach type magnetic deflection experiments on Chromium, Iron, and Aluminum clusters consisting of ˜20-200 atoms are reported. These metal clusters were produced using a laser vaporization technique in helium, and their beams were formed using supersonic expansion into vacuum. Measurements of their magnetic deflections were conducted at temperature ranging from 50K to 250K and at various magnetic field strengths. Both Chromium and Iron clusters are found to behave in accordance with a superparamagnetic model and to have enhanced magnetism compared to their bulks. For Chromium clusters with N≥34, each cluster has at least two isomers with distinguishable magnetic moments at low temperatures. For Iron clusters with Tvib=55 K, some deviations from the superparamagnetic model were observed. Aluminum clusters with odd numbers of atoms exhibit paramagnetic properties at low temperatures, which are believed to be related to superconductivity. At temperatures as low as 55K, the predicted large diamagnetism of Al56 due to superconductivity was not observed, within our system's resolution.

  16. Spectroscopic studies of nanoscale metal clusters

    NASA Astrophysics Data System (ADS)

    Gangopadhyay, P.

    2013-06-01

    The present article is intended to elucidate a range of novel spectroscopic studies of nanoscale metal clusters. Various bottom-up and top-down techniques have been utilized to synthesize the metal nanoclusters. Materials like metal nanoclusters of cobalt, silver or gold in various dielectric matrices facilitate to explore interesting phenomena through optical, photoluminescence and vibrational spectroscopy. Interaction of uv-visible light with free electrons of metal nanoclusters, for example, leads to fascinating colors of dielectric matrices through an optical effect known as surface-plasmon resonance. This effect of quantum-confinement of the electrons leads to large enhancements of local electric field in metal nanoclusters. Enhancements of Raman scattering from metal nanoclusters are attributed to the increase of local fields. Optical absorption and Raman scattering spectroscopy particularly have been highlighted here as powerful non-destructive experimental methods to study evolution of metal nanoclusters in different dielectric matrices. In relatively large metal nanoclusters, besides dipolar, quadrupolar surface-plasmon resonances have been observed.

  17. Inherent size effects on XANES of nanometer metal clusters: Size-selected platinum clusters on silica

    SciTech Connect

    Dai, Yang; Gorey, Timothy J.; Anderson, Scott L.; Lee, Sungsik; Lee, Sungwon; Seifert, Soenke; Winans, Randall E.

    2016-12-12

    X-ray absorption near-edge structure (XANES) is commonly used to probe the oxidation state of metal-containing nanomaterials, however, as the particle size in the material drops below a few nanometers, it becomes important to consider inherent size effects on the electronic structure of the materials. In this paper, we analyze a series of size-selected Ptn/SiO2 samples, using X-ray photoelectron spectroscopy (XPS), low energy ion scattering, grazing-incidence small angle X-ray scattering, and XANES. The oxidation state and morphology are characterized both as-deposited in UHV, and after air/O2 exposure and annealing in H2. Here, the clusters are found to be stable during deposition and upon air exposure, but sinter if heated above ~150 °C. XANES shows shifts in the Pt L3 edge, relative to bulk Pt, that increase with decreasing cluster size, and the cluster samples show high white line intensity. Reference to bulk standards would suggest that the clusters are oxidized, however, XPS shows that they are not. Instead, the XANES effects are attributable to development of a band gap and localization of empty state wavefunctions in small clusters.

  18. Intracellular minerals and metal deposits in prokaryotes.

    PubMed

    Edwards, K J; Bazylinski, D A

    2008-06-01

    Thanks to the work of Terrance J. Beveridge and other pioneers in the field of metal-microbe interactions, prokaryotes are well known to sequester metals and other ions intracellularly in various forms. These forms range from poorly ordered deposits of metals to well-ordered mineral crystals. Studies on well-ordered crystalline structures have generally focused on intracellular organelles produced by magnetotactic bacteria that are ubiquitous in terrestrial and marine environments that precipitate Fe(3)O(4) or Fe(3)S(4), Fe-bearing minerals that have magnetic properties and are enclosed in intracellular membranes. In contrast, studies on less-well ordered minerals have focused on Fe-, As-, Mn-, Au-, Se- and Cd-precipitates that occur intracellularly. The biological and environmental function of these particles remains a matter of debate.

  19. Atomically precise (catalytic) particles synthesized by a novel cluster deposition instrument

    DOE PAGES

    Yin, C.; Tyo, E.; Kuchta, K.; ...

    2014-05-06

    Here, we report a new high vacuum instrument which is dedicated to the preparation of well-defined clusters supported on model and technologically relevant supports for catalytic and materials investigations. The instrument is based on deposition of size selected metallic cluster ions that are produced by a high flux magnetron cluster source. Furthermore, we maximize the throughput of the apparatus by collecting and focusing ions utilizing a conical octupole ion guide and a linear ion guide. The size selection is achieved by a quadrupole mass filter. The new design of the sample holder provides for the preparation of multiple samples onmore » supports of various sizes and shapes in one session. After cluster deposition onto the support of interest, samples will be taken out of the chamber for a variety of testing and characterization.« less

  20. Atomically precise (catalytic) particles synthesized by a novel cluster deposition instrument

    SciTech Connect

    Yin, C.; Tyo, E.; Kuchta, K.; von Issendorff, B.; Vajda, S.

    2014-05-06

    Here, we report a new high vacuum instrument which is dedicated to the preparation of well-defined clusters supported on model and technologically relevant supports for catalytic and materials investigations. The instrument is based on deposition of size selected metallic cluster ions that are produced by a high flux magnetron cluster source. Furthermore, we maximize the throughput of the apparatus by collecting and focusing ions utilizing a conical octupole ion guide and a linear ion guide. The size selection is achieved by a quadrupole mass filter. The new design of the sample holder provides for the preparation of multiple samples on supports of various sizes and shapes in one session. After cluster deposition onto the support of interest, samples will be taken out of the chamber for a variety of testing and characterization.

  1. Electrophobic interaction induced impurity clustering in metals

    SciTech Connect

    Zhou, Hong-Bo; Wang, Jin-Long; Jiang, W.; Lu, Guang-Hong; Aguiar, J. A.; Liu, Feng

    2016-10-01

    We introduce the concept of electrophobic interaction, analogous to hydrophobic interaction, for describing the behavior of impurity atoms in a metal, a 'solvent of electrons'. We demonstrate that there exists a form of electrophobic interaction between impurities with closed electron shell structure, which governs their dissolution behavior in a metal. Using He, Be and Ar as examples, we predict by first-principles calculations that the electrophobic interaction drives He, Be or Ar to form a close-packed cluster with a clustering energy that follows a universal power-law scaling with the number of atoms (N) dissolved in a free electron gas, as well as W or Al lattice, as Ec is proportional to (N2/3-N). This new concept unifies the explanation for a series of experimental observations of close-packed inert-gas bubble formation in metals, and significantly advances our fundamental understanding and capacity to predict the solute behavior of impurities in metals, a useful contribution to be considered in future material design of metals for nuclear, metallurgical, and energy applications.

  2. Unusual behavior in magnesium-copper cluster matter produced by helium droplet mediated deposition

    SciTech Connect

    Emery, S. B. Little, B. K.; Xin, Y.; Ridge, C. J.; Lindsay, C. M.; Buszek, R. J.; Boatz, J. A.; Boyle, J. M.

    2015-02-28

    We demonstrate the ability to produce core-shell nanoclusters of materials that typically undergo intermetallic reactions using helium droplet mediated deposition. Composite structures of magnesium and copper were produced by sequential condensation of metal vapors inside the 0.4 K helium droplet baths and then gently deposited onto a substrate for analysis. Upon deposition, the individual clusters, with diameters ∼5 nm, form a cluster material which was subsequently characterized using scanning and transmission electron microscopies. Results of this analysis reveal the following about the deposited cluster material: it is in the un-alloyed chemical state, it maintains a stable core-shell 5 nm structure at sub-monolayer quantities, and it aggregates into unreacted structures of ∼75 nm during further deposition. Surprisingly, high angle annular dark field scanning transmission electron microscopy images revealed that the copper appears to displace the magnesium at the core of the composite cluster despite magnesium being the initially condensed species within the droplet. This phenomenon was studied further using preliminary density functional theory which revealed that copper atoms, when added sequentially to magnesium clusters, penetrate into the magnesium cores.

  3. The structure of small metal clusters

    NASA Technical Reports Server (NTRS)

    Bauschlicher, C. W., Jr.; Pettersson, L. G. M.

    1986-01-01

    One metal atom surrounded by its 12 nearest neighbors is considered for both D(3d) (face-centered cubic-like) and D(3h) (hexagonal close-packed-like) geometries. For Al and Be, the neutral cluster and the positive and negative ions are considered for idealized (all bonds equal) and distorted geometries. The D(3d) geometry is found to be the lowest for Be13, while the D(3h) geometry is lower for Al13. This is the reverse of what is expected based upon the bulk metal structures, Be(hcp) and Al(fcc). Al13 is found to have only small distortions, while Be13 shows large distortions for both the D(3d) and D(3h) geometries. The ions have geometries which are similar to those found for the neutral systems. Both all-electron and effective core potential calculations were carried out on the X13 clusters; the agreement is very good.

  4. Precursors for chemical and photochemical vapor deposition of copper metal

    NASA Astrophysics Data System (ADS)

    James, Alicia Marie

    The colorless square-planar cluster [CuN(SiMe3)2] 4, which contains four Cu(I) ions with four bridging amide groups, was studied as a precursor for chemical and photochemical vapor deposition of Cu metal. The cluster phosphoresces in CH2Cl2 solution and in the solid state at room temperature. Its electronic spectrum in CH 2Cl2 consists of two intense bands which are assigned to symmetry-allowed 3d → 4p transitions; the phosphorescence is also likely to be metal-centered. Solid [CuN(SiMe3)2]4 luminesces with approximately the same spectrum as that of the CH2Cl2 solutions. At 77 K, the solid-state luminescence red-shifts slightly. The emission lifetime in glassy Et2O solution is 690 mus. [CuN(SiMe3) 2]4 deposits Cu metal via chemical vapor deposition under H2 carrier gas at substrate temperatures of 145--200°C. Deposition also occurs photochemically beginning at 136--138°C under near-UV irradiation. The preparation of monomeric derivatives of [CuN(SiMe3) 2]4 was attempted by using neutral donor ligands L (e.g. LnCuN(SiMe3)2; L = CO, PR3, CN-t-Bu; n = 1--3). The target compounds were expected to be more volatile than the copper cluster and still maintain photosensitivity. CuCl and [Cu(CH 3CN)4]PF6 were used as starting materials. Even in the presence of L, [CuN(SiMe3)2] 4 is a major product in reactions using CuCl and NaN(SiCH3) 2- [Cu(CH3CN)4]PF6 was a promising route for the monomeric Cu(I) complexes because of ready dissociation of its acetonitrile ligands. However, the characterization of these complexes was unsuccessful. Other Cu(I) amide clusters have been prepared; they may also be suitable for chemical and photochemical vapor deposition of Cu. [CuNEt2] 4, [CuN(i-Pr)2]4, and [CuN(t-Bu)(SiMe 3)]4 are phosphorescent though they are very air sensitive. They should be more volatile and produce Cu metal films more readily than [CuN(SiMe3)2]4 Cu(hfac)2 is a versatile Lewis acid, forming adducts with a variety of bases. The bases that were used were ethylene

  5. Magnetic impurities in small metal clusters

    NASA Astrophysics Data System (ADS)

    Pastor, G. M.

    2005-09-01

    [Dedicated to Bernhard Mühlschlegel on the occasion of his 80th birthday]Magnetic impurities in small metallic clusters are investigated in the framework of the Anderson model by using exact diagonalization and geometry optimization methods.The singlet-triplet spin gap E shows a remarkable dependence as a function of band-filling, cluster structure, and impurity position that can be interpreted in terms of the environment-specific conduction-electron spectrum. The low-energy spin excitations involve similar energies as isomerizations. Interesting correlations between cluster structure and magnetic behavior are revealed. Finite-temperature properties such as specific heat, effective impurity moment, and magnetic susceptibility are calculated exactly in the canonical ensemble. A finite-size equivalent of the Kondo effect is identified and its structural dependence is discussed.

  6. Research on laser direct metal deposition

    NASA Astrophysics Data System (ADS)

    Zhang, Yongzhong; Shi, Likai

    2003-03-01

    Laser direct deposition of metallic parts is a new manufacturing technology, which combines with computer-aided design, laser cladding and rapid prototyping. Fully dense metallic parts can be directly obtained through melting the coaxially fed powders with a high-power laser in a layer-by-layer manner. The process characteristics, system composition as well as some research and advancement on laser direct deposition are presented here. The microstructure and properties observation of laser direct formed 663 copper alloy, 316L stainless steel and Rene'95 nickel super alloy samples indicate that, the as-deposited microstructure is similar to rapidly solidified materials, with homogenous composition and free of defects. Under certain conditions, directionally solidified microstructure can be obtained. The as-formed mechanical properties are equal to or exceed those for casting and wrought annealed materials. At the same time, some sample parts with complicate shape are presented for technology demonstration. The formed parts show good surface quality and dimensional accuracy.

  7. Growth of Metal Nano-Clusters on Metal and Oxide Surfaces:. a Rheed Study

    NASA Astrophysics Data System (ADS)

    Zei, M. S.

    The powerful RHEED technique has been demonstrated for the structural determination of the nano-crystals grown on metal and oxide substrate surfaces. Pt was electrochemically deposited onto a Ru(10bar {1}0) electrode, while Pb and cobalt were vapor deposited onto Ag(111) and oxide film/NiAl(100), respectively under UHV conditions. At any Pt coverage, 3D-clusters develop for which the Pt clusters grow in (311) orientation on the Ru(10bar {1}0) substrate surface, where the [01bar {1}] atomic rows of the (311) facet are parallel to the [1bar {2}10] atomic rows of the Ru(10bar {1}0) surface. Due to the strong bonding at Pb/Ag(111) interface, the Pb deposit grows in 2D-islands with a (√ {3} × √ {3})R30o phase (Θ < 1 ML). On the other hand, the β-crystallites of ≈ 1 nm in diameter with inclusion of smaller-sized particles (D < 1 nm) are observed on Θ-Al2O3 after Co deposition at room temperature. Annealing at 900 K Co clusters (≈ 3 nm) grow larger at expense of small particles on thin oxide film on NiAl(100) and become better ordered, where the [110] axis of the Co(001) facet is parallel to the [100] direction of the (001)-oxide surface. The in-plane lattice constant of Co clusters is ca. 4 larger than that of bulk Co, yielding less strain at the (001)-oxide surface. These results demonstrate that both orientation and phase of metal nano-clusters are governed by surface structure of the substrate.

  8. Spectroscopy at metal cluster surfaces. Annual report, Year 2

    SciTech Connect

    Duncan, M.A.

    1995-08-01

    The focus of our research program is the study of gas phase metal clusters to evaluate their potential to model fundamental interactions present on metal surfaces. To do this, we characterize the chemical bonding present between the component atoms in metal clusters as well as the bonding exhibited by ``physisorption`` on cluster surfaces. Electronic spectra, vibrational frequencies and bond neutral and ionized clusters with a variety of laser/mass spectrometry techniques. We are particularly interested in bimetallic cluster systems, and how their properties compare to those of corresponding pure metal clusters.

  9. Structure stability and spectroscopy of metal clusters. Progress report

    SciTech Connect

    Not Available

    1993-06-01

    Theory based on self-consistent field-linear combinations of atomic orbitals-molecular orbital theory was applied to clusters. Four areas were covered: electronic structure, equilibrium geometries, and stability of charged clusters, interaction of metal clusters with H and halogen atoms, thermal stability of isolated clusters, and stability and optical properties of hetero-atomic clusters. (DLC)

  10. Dynamics of transition-metal clusters

    NASA Astrophysics Data System (ADS)

    Sawada, S.; Sugano, S.

    1989-03-01

    The atomic structure and thermodynamic properties of transition-metal 6- and 7-atom clusters are investigated using the molecular dynamics method, where Gupta's potential taking into account many-body interaction is employed. The caloric and the structural fluctuations are studied. The “fluctuating state” is found for N=6 in the region of the temperature near and below the melting point, where clusters undergo structural transition from one isomer to others without making any topological change. The fluctuating state differs from the “coexistence state” found in Ar clusters [1] i.e. the former involves no liquid state. In the liquid state the motion of atom-permutation occurs besides the breathing motion. On the other hand, the fluctuating state is not found for N=7 but only the motion of atom-permutation in the liquid state. The coexistence state is found in both cases of 6- and 7-atom clusters. We also discuss a possibility of larger clusters displaying the fluctuating state.

  11. Heavy metal atmospheric deposition and biomonitoring

    NASA Astrophysics Data System (ADS)

    Ayrault, S.; Clocchiatti, R.; Carrot, F.; Michel, A.; Gaudry, A.; Moskura, M.

    2003-05-01

    The atmospheric fluxes of heavy metals were measured continuously in the Paris area. The dry depositions were collected on quartz fiber filters, after comparison between clogging capacities and blank levels on commercial filters. Rain was collected in a polyethylene gauge. Two transplanted biomonitors, the epiphytic lichen Evernia prunastri, and the pleurocarpeous moss Scleropodium purum, were exposed simultaneously. These two common biomonitors have been used in previous passive biomonitoring campaigns [Galsomies 1999, Grasso 1999]. This work attempts to produce data on heavy metal exposure of this populated area near Paris, and to compare these two cryptogamic species behaviour. The results on bioaccumulation were compared to those given by a previous work in Italy [Bargagli, 2002] comparing the moss Hypnum cupressiforme and the lichen Parmelia caperata. In our study, the transplanted lichens were exposed in different conditions: to the rain or protected from rain, in vertical, horizontal or oblique position. Dry (filters) and wet (rain) depositions and biomonitors were analysed by Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) and Neutron Activation Analysis (NAA) for more than 30elements [Ayrault, 2001]. The individual particle composition (on filters and cryptogams) was determined by nuclear microprobe (PIXE) and electron microprobe. The lichens displayed different accumulation rates, depending on exposition conditions. In particular, the inclination influenced the bulk concentrations in the lichen. Relation was made between fluxes and concentration accumulated by the biomonitors. The enrichment factors were spectacular for some elements, e.g. lead.

  12. A Study of Deposition Coatings Formed by Electroformed Metallic Materials

    PubMed Central

    Shimura, Kojiro; Tobayama, Go; Togashi, Toshio

    2016-01-01

    Major joining methods of dental casting metal include brazing and laser welding. However, brazing cannot be applied for electroformed metals since heat treatment could affect the fit, and, therefore, laser welding is used for such metals. New methods of joining metals that do not impair the characteristics of electroformed metals should be developed. When new coating is performed on the surface of the base metal, surface treatment is usually performed before re-coating. The effect of surface treatment is clinically evaluated by peeling and flex tests. However, these testing methods are not ideal for deposition coating strength measurement of electroformed metals. There have been no studies on the deposition coating strength and methods to test electroformed metals. We developed a new deposition coating strength test for electroformed metals. The influence of the negative electrolytic method, which is one of the electrochemical surface treatments, on the strength of the deposition coating of electroformed metals was investigated, and the following conclusions were drawn: 1. This process makes it possible to remove residual deposits on the electrodeposited metal surface layer. 2. Cathode electrolysis is a simple and safe method that is capable of improving the surface treatment by adjustments to the current supply method and current intensity. 3. Electrochemical treatment can improve the deposition coating strength compared to the physical or chemical treatment methods. 4. Electro-deposition coating is an innovative technique for the deposition coating of electroformed metal. PMID:27326757

  13. A Study of Deposition Coatings Formed by Electroformed Metallic Materials.

    PubMed

    Hayashi, Shoji; Sugiyama, Shuta; Shimura, Kojiro; Tobayama, Go; Togashi, Toshio

    2016-01-01

    Major joining methods of dental casting metal include brazing and laser welding. However, brazing cannot be applied for electroformed metals since heat treatment could affect the fit, and, therefore, laser welding is used for such metals. New methods of joining metals that do not impair the characteristics of electroformed metals should be developed. When new coating is performed on the surface of the base metal, surface treatment is usually performed before re-coating. The effect of surface treatment is clinically evaluated by peeling and flex tests. However, these testing methods are not ideal for deposition coating strength measurement of electroformed metals. There have been no studies on the deposition coating strength and methods to test electroformed metals. We developed a new deposition coating strength test for electroformed metals. The influence of the negative electrolytic method, which is one of the electrochemical surface treatments, on the strength of the deposition coating of electroformed metals was investigated, and the following conclusions were drawn: 1. This process makes it possible to remove residual deposits on the electrodeposited metal surface layer. 2. Cathode electrolysis is a simple and safe method that is capable of improving the surface treatment by adjustments to the current supply method and current intensity. 3. Electrochemical treatment can improve the deposition coating strength compared to the physical or chemical treatment methods. 4. Electro-deposition coating is an innovative technique for the deposition coating of electroformed metal.

  14. Inherent size effects on XANES of nanometer metal clusters: Size-selected platinum clusters on silica

    DOE PAGES

    Dai, Yang; Gorey, Timothy J.; Anderson, Scott L.; ...

    2016-12-12

    X-ray absorption near-edge structure (XANES) is commonly used to probe the oxidation state of metal-containing nanomaterials, however, as the particle size in the material drops below a few nanometers, it becomes important to consider inherent size effects on the electronic structure of the materials. In this paper, we analyze a series of size-selected Ptn/SiO2 samples, using X-ray photoelectron spectroscopy (XPS), low energy ion scattering, grazing-incidence small angle X-ray scattering, and XANES. The oxidation state and morphology are characterized both as-deposited in UHV, and after air/O2 exposure and annealing in H2. Here, the clusters are found to be stable during depositionmore » and upon air exposure, but sinter if heated above ~150 °C. XANES shows shifts in the Pt L3 edge, relative to bulk Pt, that increase with decreasing cluster size, and the cluster samples show high white line intensity. Reference to bulk standards would suggest that the clusters are oxidized, however, XPS shows that they are not. Instead, the XANES effects are attributable to development of a band gap and localization of empty state wavefunctions in small clusters.« less

  15. Metallic nanoparticle deposition techniques for enhanced organic photovoltaic cells

    NASA Astrophysics Data System (ADS)

    Cacha, Brian Joseph Gonda

    Energy generation via organic photovoltaic (OPV) cells provide many advantages over alternative processes including flexibility and price. However, more efficient OPVs are required in order to be competitive for applications. One way to enhance efficiency is through manipulation of exciton mechanisms within the OPV, for example by inserting a thin film of bathocuproine (BCP) and gold nanoparticles between the C60/Al and ZnPc/ITO interfaces, respectively. We find that BCP increases efficiencies by 330% due to gains of open circuit voltage (Voc) by 160% and short circuit current (Jsc) by 130%. However, these gains are complicated by the anomalous photovoltaic effect and an internal chemical potential. Exploration in the tuning of metallic nanoparticle deposition on ITO was done through four techniques. Drop casting Ag nanoparticle solution showed arduous control on deposited morphology. Spin-coating deposited very low densities of nanoparticles. Drop casting and spin-coating methods showed arduous control on Ag nanoparticle morphology due to clustering and low deposition density, respectively. Sputtered gold on glass was initially created to aid the adherence of Ag nanoparticles but instead showed a quick way to deposit aggregated gold nanoparticles. Electrodeposition of gold nanoparticles (AuNP) proved a quick method to tune nanoparticle morphology on ITO substrates. Control of deposition parameters affected AuNP size and distribution. AFM images of electrodeposited AuNPs showed sizes ranging from 39 to 58 nm. UV-Vis spectroscopy showed the presence of localized plasmon resonance through absorption peaks ranging from 503 to 614 nm. A linear correlation between electrodeposited AuNP size and peak absorbance was seen with a slope of 3.26 wavelength(nm)/diameter(nm).

  16. The chemistry and physics of transition metal clusters

    SciTech Connect

    Parks, E.K.; Jellinek, J.; Knickelbein, M.B.; Riley, S.J.

    1994-06-01

    In this program the authors study the fundamental properties of isolated clusters of transition metal atoms. Experimental studies of cluster chemistry include determination of cluster structure, reactivity, and the nature of cluster-adsorbate interactions. Studies of physical properties include measurements of cluster ionization potentials and photoabsorption cross sections. Theoretical studies focus on the structure and dynamics of clusters, including isomers, phases and phase changes, interactions with molecules, and fragmentation process.

  17. Determination of Globular Cluster metallicities with BUSCA

    NASA Astrophysics Data System (ADS)

    Wittlich, M.; Cordes, O.; Reif, K.

    Globular Clusters (GCs) have always been a topic of great interest probing stellar and galactic evolution. This includes both determination of age and metallicity. The stars in GCs are known to be more or less coeval and therefore considered to be formed out of the same primordial cloud, implying same chemical composition. Deriving metallicities yields indicators for primordial enrichment of the GC forming cloud. Recent studies show abundance differences among GC giants (Kraft 1994). The spread in abundances tends to be correlated with oxygen and CN-band strengths, resulting in new differing formation and evolution scenarios for GC. Strömgren photometry is known to be an adequate method for metallicity determination (Strömgren 1966). In this poster, we present preliminary results of metallicity studies in the Strömgren uvby-Hβ colour system for a sample of bright GCs. The data were obtained with BUSCA (``Bonn University Simultaneous CAmera''), the new 4k×4k CCD 4-colour imaging instrument at the 2.2m telescope at Calar Alto Observatory. The observed GC were selected relying on a wide spread in mean GC metallicities to obtain hints on their formation process. Photometric reduction was conducted using the package DAOPHOT of the IRAF program. Standard stars for calibration were chosen according to Olsen & Perry (1987). A revised Strömgren metallicity calibration for red giants proposed by Hilker (2000) was applied to the data to detect CN variations. In connection with spectroscopy from literature we are able to argue whether the CN variations are triggered by primordial abundance variations or by evolutionary mixing processes.

  18. Metal Adatoms and Clusters on Ultrathin Zirconia Films

    PubMed Central

    2016-01-01

    Nucleation and growth of transition metals on zirconia has been studied by scanning tunneling microscopy (STM) and density functional theory (DFT) calculations. Since STM requires electrical conductivity, ultrathin ZrO2 films grown by oxidation of Pt3Zr(0001) and Pd3Zr(0001) were used as model systems. DFT studies were performed for single metal adatoms on supported ZrO2 films as well as the (1̅11) surface of monoclinic ZrO2. STM shows decreasing cluster size, indicative of increasing metal–oxide interaction, in the sequence Ag < Pd ≈ Au < Ni ≈ Fe. Ag and Pd nucleate mostly at steps and domain boundaries of ZrO2/Pt3Zr(0001) and form three-dimensional clusters. Deposition of low coverages of Ni and Fe at room temperature leads to a high density of few-atom clusters on the oxide terraces. Weak bonding of Ag to the oxide is demonstrated by removing Ag clusters with the STM tip. DFT calculations for single adatoms show that the metal–oxide interaction strength increases in the sequence Ag < Au < Pd < Ni on monoclinic ZrO2, and Ag ≈ Au < Pd < Ni on the supported ultrathin ZrO2 film. With the exception of Au, metal nucleation and growth on ultrathin zirconia films follow the usual rules: More reactive (more electropositive) metals result in a higher cluster density and wet the surface more strongly than more noble metals. These bind mainly to the oxygen anions of the oxide. Au is an exception because it can bind strongly to the Zr cations. Au diffusion may be impeded by changing its charge state between −1 and +1. We discuss differences between the supported ultrathin zirconia films and the surfaces of bulk ZrO2, such as the possibility of charge transfer to the substrate of the films. Due to their large in-plane lattice constant and the variety of adsorption sites, ZrO2{111} surfaces are more reactive than many other oxygen-terminated oxide surfaces. PMID:27213024

  19. Metal etching with reactive gas cluster ion beams using pickup cell

    SciTech Connect

    Toyoda, Noriaki; Yamada, Isao

    2012-11-06

    Mixed gas cluster ion beams were formed using pickup cell for metal etching. O{sub 2} neutral clusters pick up acetic acid and formed mixed cluster beam. By using O{sub 2}-GCIB with acetic acid, enhancement of Cu etching was observed. Because of dense energy deposition by GCIB, etching of Cu proceeds by CuO formation, enhancement of chemical reaction with acetic acid and desorption of etching products. Surface roughening was not observed on poly crystalline Cu because of the small dependence of etching rate on crystal orientation. Halogen free and low-temperature metal etching with GCIB using pickup cell is possible.

  20. Growth modes of thin films of ligand-free metal clusters

    SciTech Connect

    Dollinger, A.; Strobel, C. H.; Bleuel, H.; Marsteller, A.; Gantefoer, G.; Fairbrother, D. H.; Tang, Xin; Bowen, K. H.; Kim, Young Dok

    2015-05-21

    Size-selected Mo{sub n}{sup −}, W{sub n}{sup −}, and Fe{sub n}{sup −} cluster anions are deposited on a weakly interacting substrate (highly oriented pyrolytic graphite) and studied ex-situ using atomic force microscopy. Depending on size, three growth modes can be distinguished. Very small clusters consisting of less than 10–30 atoms behave similar to atoms and coalesce into 3-dimensional bulk-like islands. Medium sized clusters consisting of hundreds of atoms do not coalesce and follow a Stanski-Krastanov growth pattern. At low coverage, an almost perfect monolayer is formed. This is a new finding different from all previous studies on deposited metal clusters. For clusters with several thousands of atoms, the growth pattern again changes. At low coverage, the substrate is dotted with individual clusters, while at high coverage, the surface becomes extremely rough.

  1. Atomic layer deposition of metal sulfide materials.

    PubMed

    Dasgupta, Neil P; Meng, Xiangbo; Elam, Jeffrey W; Martinson, Alex B F

    2015-02-17

    CONSPECTUS: The field of nanoscience is delivering increasingly intricate yet elegant geometric structures incorporating an ever-expanding palette of materials. Atomic layer deposition (ALD) is a powerful driver of this field, providing exceptionally conformal coatings spanning the periodic table and atomic-scale precision independent of substrate geometry. This versatility is intrinsic to ALD and results from sequential and self-limiting surface reactions. This characteristic facilitates digital synthesis, in which the film grows linearly with the number of reaction cycles. While the majority of ALD processes identified to date produce metal oxides, novel applications in areas such as energy storage, catalysis, and nanophotonics are motivating interest in sulfide materials. Recent progress in ALD of sulfides has expanded the diversity of accessible materials as well as a more complete understanding of the unique chalcogenide surface chemistry. ALD of sulfide materials typically uses metalorganic precursors and hydrogen sulfide (H2S). As in oxide ALD, the precursor chemistry is critical to controlling both the film growth and properties including roughness, crystallinity, and impurity levels. By modification of the precursor sequence, multicomponent sulfides have been deposited, although challenges remain because of the higher propensity for cation exchange reactions, greater diffusion rates, and unintentional annealing of this more labile class of materials. A deeper understanding of these surface chemical reactions has been achieved through a combination of in situ studies and quantum-chemical calculations. As this understanding matures, so does our ability to deterministically tailor film properties to new applications and more sophisticated devices. This Account highlights the attributes of ALD chemistry that are unique to metal sulfides and surveys recent applications of these materials in photovoltaics, energy storage, and photonics. Within each application

  2. Atomic layer deposition of metal sulfide materials

    DOE PAGES

    Dasgupta, Neil P.; Meng, Xiangbo; Elam, Jeffrey W.; ...

    2015-01-12

    The field of nanoscience is delivering increasingly intricate yet elegant geometric structures incorporating an ever-expanding palette of materials. Atomic layer deposition (ALD) is a powerful driver of this field, providing exceptionally conformal coatings spanning the periodic table and atomic-scale precision independent of substrate geometry. This versatility is intrinsic to ALD and results from sequential and self-limiting surface reactions. This characteristic facilitates digital synthesis, in which the film grows linearly with the number of reaction cycles. While the majority of ALD processes identified to date produce metal oxides, novel applications in areas such as energy storage, catalysis, and nanophotonics are motivatingmore » interest in sulfide materials. Recent progress in ALD of sulfides has expanded the diversity of accessible materials as well as a more complete understanding of the unique chalcogenide surface chemistry. ALD of sulfide materials typically uses metalorganic precursors and hydrogen sulfide (H2S). As in oxide ALD, the precursor chemistry is critical to controlling both the film growth and properties including roughness, crystallinity, and impurity levels. By modification of the precursor sequence, multicomponent sulfides have been deposited, although challenges remain because of the higher propensity for cation exchange reactions, greater diffusion rates, and unintentional annealing of this more labile class of materials. A deeper understanding of these surface chemical reactions has been achieved through a combination of in situ studies and quantum-chemical calculations. As this understanding matures, so does our ability to deterministically tailor film properties to new applications and more sophisticated devices. This Account highlights the attributes of ALD chemistry that are unique to metal sulfides and surveys recent applications of these materials in photovoltaics, energy storage, and photonics. Within each application space

  3. Atomic Layer Deposition of Metal Sulfide Materials

    SciTech Connect

    Dasgupta, Neil P.; Meng, Xiangbo; Elam, Jeffrey W.; Martinson, Alex B. F.

    2015-02-17

    The field of nanoscience is delivering increasingly intricate yet elegant geometric structures incorporating an ever-expanding palette of materials. Atomic layer deposition (ALD) is a powerful driver of this field, providing exceptionally conformal coatings spanning the periodic table and atomic-scale precision independent of substrate geometry. This versatility is intrinsic to ALD and results from sequential and self-limiting surface reactions. This characteristic facilitates digital synthesis, in which the film grows linearly with the number of reaction cycles. While the majority of ALD processes identified to date produce metal oxides, novel applications in areas such as energy storage, catalysis, and nanophotonics are motivating interest in sulfide materials. Recent progress in ALD of sulfides has expanded the diversity of accessible materials as well as a more complete understanding of the unique chalcogenide surface chemistry.

  4. Programmable nanometer-scale electrolytic metal deposition and depletion

    DOEpatents

    Lee, James Weifu [Oak Ridge, TN; Greenbaum, Elias [Oak Ridge, TN

    2002-09-10

    A method of nanometer-scale deposition of a metal onto a nanostructure includes the steps of: providing a substrate having thereon at least two electrically conductive nanostructures spaced no more than about 50 .mu.m apart; and depositing metal on at least one of the nanostructures by electric field-directed, programmable, pulsed electrolytic metal deposition. Moreover, a method of nanometer-scale depletion of a metal from a nanostructure includes the steps of providing a substrate having thereon at least two electrically conductive nanostructures spaced no more than about 50 .mu.m apart, at least one of the nanostructures having a metal disposed thereon; and depleting at least a portion of the metal from the nanostructure by electric field-directed, programmable, pulsed electrolytic metal depletion. A bypass circuit enables ultra-finely controlled deposition.

  5. Sputter deposition of metallic thin film and directpatterning

    SciTech Connect

    Ji, L.; Chen, Y.; Jiang, X.; Ji, Q.; Leung, K.-N.

    2005-09-09

    A compact apparatus is developed for deposition of metal thin film. The system employs an RF discharge plasma source with a straight RF antenna, which is made of or covered with deposition material, serving as sputtering target at the same time. The average deposition rate of copper thin film is as high as 450nm/min. By properly allocating the metal materials on the sputtering antenna, mixture deposition of multiple metal species is achieved. Using an ion beam imprinting scheme also taking advantage of ion beam focusing technique, two different schemes of direct patterning deposition process are developed: direct depositing patterned metallic thin film and resistless ion beam sputter patterning. Preliminary experiments have demonstrated direct pattern transfer from a template with feature size of micro scale; patterns with more than 10x reduction are achieved by sputtering patterning method.

  6. On the metallicity of open clusters. III. Homogenised sample

    NASA Astrophysics Data System (ADS)

    Netopil, M.; Paunzen, E.; Heiter, U.; Soubiran, C.

    2016-01-01

    Context. Open clusters are known as excellent tools for various topics in Galactic research. For example, they allow accurately tracing the chemical structure of the Galactic disc. However, the metallicity is known only for a rather low percentage of the open cluster population, and these values are based on a variety of methods and data. Therefore, a large and homogeneous sample is highly desirable. Aims: In the third part of our series we compile a large sample of homogenised open cluster metallicities using a wide variety of different sources. These data and a sample of Cepheids are used to investigate the radial metallicity gradient, age effects, and to test current models. Methods: We used photometric and spectroscopic data to derive cluster metallicities. The different sources were checked and tested for possible offsets and correlations. Results: In total, metallicities for 172 open cluster were derived. We used the spectroscopic data of 100 objects for a study of the radial metallicity distribution and the age-metallicity relation. We found a possible increase of metallicity with age, which, if confirmed, would provide observational evidence for radial migration. Although a statistical significance is given, more studies are certainly needed to exclude selection effects, for example. The comparison of open clusters and Cepheids with recent Galactic models agrees well in general. However, the models do not reproduce the flat gradient of the open clusters in the outer disc. Thus, the effect of radial migration is either underestimated in the models, or an additional mechanism is at work. Conclusions: Apart from the Cepheids, open clusters are the best tracers for metallicity over large Galactocentric distances in the Milky Way. For a sound statistical analysis, a sufficiently large and homogeneous sample of cluster metallicities is needed. Our compilation is currently by far the largest and provides the basis for several basic studies such as the statistical

  7. Molecular dynamical simulations of melting behaviors of metal clusters

    SciTech Connect

    Hamid, Ilyar; Fang, Meng; Duan, Haiming

    2015-04-15

    The melting behaviors of metal clusters are studied in a wide range by molecular dynamics simulations. The calculated results show that there are fluctuations in the heat capacity curves of some metal clusters due to the strong structural competition; For the 13-, 55- and 147-atom clusters, variations of the melting points with atomic number are almost the same; It is found that for different metal clusters the dynamical stabilities of the octahedral structures can be inferred in general by a criterion proposed earlier by F. Baletto et al. [J. Chem. Phys. 116 3856 (2002)] for the statically stable structures.

  8. Y-Ba-Cu-O film deposition by metal organic chemical vapor deposition on buffered metal substrates.

    SciTech Connect

    Selvamanickam, V.; Galinski, G.; DeFrank, J.; Trautwein, C.; Haldar, P.; Balachandran, U.; Lanagan, M.; Chudzik, M.

    1999-10-12

    YBa{sub 2}Cu{sub 3}O{sub 2} (YBCO) films have been deposited on buffered metal substrates by Metal Organic Chemical Vapor Deposition (MOCVD). Cube-textured nickel substrates were fabricated by a thermomechanical process. Epitaxial CeO{sub 2}films were deposited on these substrates by thermal evaporation. Nickel alloy substrates with biaxially-textured Yttria-Stabilized Zirconia (YSZ) buffer layers deposited by Ion Beam Assisted Deposition were also prepared. Highly biaxially-textured YBCO films were deposited by MOCVD on both types of metal substrates. A critical current density greater than 10{sup 5} A/cm{sup 2} at 77 K has been achieved in YBCO films on metal substrates.

  9. Polymer-assisted aqueous deposition of metal oxide films

    DOEpatents

    Li, DeQuan [Los Alamos, NM; Jia, Quanxi [Los Alamos, NM

    2003-07-08

    An organic solvent-free process for deposition of metal oxide thin films is presented. The process includes aqueous solutions of necessary metal precursors and an aqueous solution of a water-soluble polymer. After a coating operation, the resultant coating is fired at high temperatures to yield optical quality metal oxide thin films.

  10. The deposition and fate of trace metals in our environment.

    Treesearch

    Elon S. Verry; Stephen J. Vermette

    1992-01-01

    This proceedings contains 14 invited papers from Canada and the United States on trace metal emissions, trace metal measurement in precipitation and dry fall, regional deposition, and the fate of trace metals in soils, plants, waters, and fish. A summary paper integrates the major findings of each paper.

  11. Vapor Deposition Of Metal From Gas/Tungsten Arc

    NASA Technical Reports Server (NTRS)

    Weeks, Jack L.; Poorman, Richard M.

    1992-01-01

    Vacuum gas/tungsten-arc vapor-deposition process yields highly reflective, smooth films reproducing contours of surfaces on which deposited. Rate of deposition controlled precisely, and surface texture varied. Capable of deposition at rates double those of standard sputtering. Useful in making thin metallic coats to serve as electrical conductors, radio reflectors or antenna elements, or optical mirrors of partial or ultrahigh reflectivity, and in making semiconductor devices.

  12. Formation of amorphous metal alloys by chemical vapor deposition

    DOEpatents

    Mullendore, Arthur W.

    1990-01-01

    Amorphous alloys are deposited by a process of thermal dissociation of mixtures or organometallic compounds and metalloid hydrides, e.g., transition metal carbonyl such as nickel carbonyl, and diborane. Various sizes and shapes of deposits can be achieved, including near-net-shape free standing articles, multilayer deposits, and the like. Manipulation or absence of a magnetic field affects the nature and the structure of the deposit.

  13. Formation of amorphous metal alloys by chemical vapor deposition

    DOEpatents

    Mullendore, A.W.

    1988-03-18

    Amorphous alloys are deposited by a process of thermal dissociation of mixtures of organometallic compounds and metalloid hydrides,e.g., transition metal carbonyl, such as nickel carbonyl and diborane. Various sizes and shapes of deposits can be achieved, including near-net-shape free standing articles, multilayer deposits, and the like. Manipulation or absence of a magnetic field affects the nature and the structure of the deposit. 1 fig.

  14. Vapor Deposition Of Metal From Gas/Tungsten Arc

    NASA Technical Reports Server (NTRS)

    Weeks, Jack L.; Poorman, Richard M.

    1992-01-01

    Vacuum gas/tungsten-arc vapor-deposition process yields highly reflective, smooth films reproducing contours of surfaces on which deposited. Rate of deposition controlled precisely, and surface texture varied. Capable of deposition at rates double those of standard sputtering. Useful in making thin metallic coats to serve as electrical conductors, radio reflectors or antenna elements, or optical mirrors of partial or ultrahigh reflectivity, and in making semiconductor devices.

  15. Graphdiyne oxides as excellent substrate for electroless deposition of Pd clusters with high catalytic activity.

    PubMed

    Qi, Hetong; Yu, Ping; Wang, Yuexiang; Han, Guangchao; Liu, Huibiao; Yi, Yuanping; Li, Yuliang; Mao, Lanqun

    2015-04-29

    Graphdiyne (GDY), a novel kind of two-dimensional carbon allotrope consisting of sp- and sp(2)-hybridized carbon atoms, is found to be able to serve as the reducing agent and stabilizer for electroless deposition of highly dispersed Pd nanoparticles owing to its low reduction potential and highly conjugated electronic structure. Furthermore, we observe that graphdiyne oxide (GDYO), the oxidation form of GDY, can be used as an even excellent substrate for electroless deposition of ultrafine Pd clusters to form Pd/GDYO nanocomposite that exhibits a high catalytic performance toward the reduction of 4-nitrophenol. The high catalytic performance is considered to benefit from the rational design and electroless deposition of active metal catalysts with GDYO as the support.

  16. Cluster-assembled Tb-Fe nanostructured films produced by low energy cluster beam deposition.

    PubMed

    Zhao, Shifeng; Bi, Feng; Wan, Jian-Guo; Han, Min; Song, Fengqi; Liu, Jun-Ming; Wang, Guanghou

    2007-07-04

    Cluster-assembled Tb-Fe nanostructured films were prepared by the low energy cluster beam deposition method. The microstructure, magnetization and magnetostriction were investigated for the films. It is shown that the film is assembled by monodisperse spherical nanoparticles with average diameter of ∼30 nm which are distributed uniformly. The cluster-assembled Tb-Fe nanostructured films exhibit good magnetization and possess giant magnetostriction with saturation value of ∼1060 × 10(-6), much higher than that of the common Tb-Fe films. The origin of good magnetization and giant magnetostriction for the cluster-assembled Tb-Fe nanostructured film was discussed. The present work opens a new avenue to produce the nanostructured magnetostrictive alloy in application of a nano-electro-mechanical system.

  17. Metal film deposition by laser breakdown chemical vapor deposition

    SciTech Connect

    Jervis, T.R.

    1985-01-01

    Dielectric breakdown of gas mixtures can be used to deposit homogeneous thin films by chemical vapor deposition with appropriate control of flow and pressure conditions to suppress gas phase nucleation and particle formation. Using a pulsed CO/sub 2/ laser operating at 10.6 microns where there is no significant resonant absorption in any of the source gases, we have succeeded in depositing homogeneous films from several gas phase precursors by gas phase laser pyrolysis. Nickel and molybdenum from the respective carbonyls and tungsten from the hexafluoride have been examined to date. In each case the gas precursor is buffered to reduce the partial pressure of the reactants and to induce breakdown. The films are spectrally reflective and uniform over a large area. Films have been characterized by Auger electron spectroscopy, x-ray diffraction, pull tests, and resistivity measurements. The highest quality films have resulted from the nickel depositions. Detailed x-ray diffraction analysis of these films yields a very small domain size (approx. 50 A) consistent with rapid quenching from the gas phase reaction zone. This analysis also shows nickel carbide formation consistent with the temperature of the reaction zone and the Auger electron spectroscopy results which show some carbon and oxygen incorporation (8% and 1% respectively). Gas phase transport and condensation of the molybdenum carbonyl results in substantial carbon and oxygen contamination of the molybdenum films requiring heated substrates, a requirement not consistent with the goals of the program to maximize the quench rate of the deposition. Results from tungsten deposition experiments representing a reduction chemistry instead of the decomposition chemistry involved in the carbonyl experiments are also reported.

  18. Metal film deposition by laser breakdown chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Jervis, T. R.

    1985-01-01

    Dielectric breakdown of gas mixtures can be used to deposit homogeneous thin films by chemical vapor deposition with appropriate control of flow and pressure conditions to suppress gas phase nucleation and particle formation. Using a pulsed CO2 laser operating at 10.6 microns where there is no significant resonant absorption in any of the source gases, we have succeeded in depositing homogeneous films from several gas phase precursors by gas phase laser pyrolysis. Nickel and molybdenum from the respective carbonyls and tungsten from the hexafluoride have been examined to date. In each case the gas precursor is buffered to reduce the partial pressure of the reactants and to induce breakdown. The films are spectrally reflective and uniform over a large area. Films have been characterized by Auger electron spectroscopy, X-ray diffraction, pull tests, and resistivity measurements. The highest quality films have resulted from the nickel depositions. Detailed X-ray diffraction analysis of these films yields a very small domain size (approx. 50 A) consistent with rapid quenching from the gas phase reaction zone. This analysis also shows nickel carbide formation consistent with the temperature of the reaction zone and the Auger electron spectroscopy results which show some carbon and oxygen incorporation (8% and 1% respectively). Gas phase transport and condensation of the molybdenum carbonyl results in substantial carbon and oxygen contamination of the molybdenum films requiring heated substrates, a requirement not consistent with the goals of the program to maximize the quench rate of the deposition. Results from tungsten deposition experiments representing a reduction chemistry instead of the decomposition chemistry involved in the carbonyl experiments are also reported.

  19. Electronic Structure and Geometries of Small Compound Metal Clusters

    SciTech Connect

    1999-04-14

    During the tenure of the DOE grant DE-FG05-87EI145316 we have concentrated on equilibrium geometries, stability, and the electronic structure of transition metal-carbon clusters (met-cars), clusters designed to mimic the chemistry of atoms, and reactivity of homo-nuclear metal clusters and ions with various reactant molecules. It is difficult to describe all the research the authors have accomplished as they have published 38 papers. In this report, they outline briefly the salient features of their work on the following topics: (1) Designer Clusters: Building Blocks for a New Class of Solids; (2) Atomic Structure, Stability, and Electronic Properties of Metallo-Carbohedrenes; (3) Reactivity of Metal Clusters with H{sub 2} and NO; and (4) Anomalous Spectroscopy of Li{sub 4} Clusters.

  20. Gas phase metal cluster model systems for heterogeneous catalysis.

    PubMed

    Lang, Sandra M; Bernhardt, Thorsten M

    2012-07-14

    Since the advent of intense cluster sources, physical and chemical properties of isolated metal clusters are an active field of research. In particular, gas phase metal clusters represent ideal model systems to gain molecular level insight into the energetics and kinetics of metal-mediated catalytic reactions. Here we summarize experimental reactivity studies as well as investigations of thermal catalytic reaction cycles on small gas phase metal clusters, mostly in relation to the surprising catalytic activity of nanoscale gold particles. A particular emphasis is put on the importance of conceptual insights gained through the study of gas phase model systems. Based on these concepts future perspectives are formulated in terms of variation and optimization of catalytic materials e.g. by utilization of bimetals and metal oxides. Furthermore, the future potential of bio-inspired catalytic material systems are highlighted and technical developments are discussed.

  1. Metal film deposition by laser breakdown chemical vapor deposition

    SciTech Connect

    Jervis, T. R.; Newkirk, L. R.

    1986-06-01

    Dielectric breakdown of gas mixtures can be used to deposit thin films by chemical vapor deposition with appropriate control of flow and pressure conditions to suppress gas-phase nucleation and particle formation. Using a pulsed CO/sub 2/ laser operating at 10.6 ..mu.. where there is no significant resonant absorption in any of the source gases, homogeneous films from several gas-phase precursors have been sucessfully deposited by gas-phase laser pyrolysis. Nickel and molybdenum from the respective carbonyls representing decomposition chemistry and tungsten from the hexafluoride representing reduction chemistry have been demonstrated. In each case the gas precursor is buffered with argon to reduce the partial pressure of the reactants and to induce breakdown. Films have been characterized by Auger electron spectroscopy, x-ray diffraction, transmission electron microscopy, pull tests, and resistivity measurements. The highest quality films have resulted from the nickel depositions. Detailed x-ray diffraction analysis of these films yields a very small domain size consistent with the low temperature of the substrate and the formation of metastable nickel carbide. Transmission electron microscopy supports this analysis.

  2. Polymer-assisted deposition of metal-oxide films.

    PubMed

    Jia, Q X; McCleskey, T M; Burrell, A K; Lin, Y; Collis, G E; Wang, H; Li, A D Q; Foltyn, S R

    2004-08-01

    Metal oxides are emerging as important materials for their versatile properties such as high-temperature superconductivity, ferroelectricity, ferromagnetism, piezoelectricity and semiconductivity. Metal-oxide films are conventionally grown by physical and chemical vapour deposition. However, the high cost of necessary equipment and restriction of coatings on a relatively small area have limited their potential applications. Chemical-solution depositions such as sol-gel are more cost-effective, but many metal oxides cannot be deposited and the control of stoichiometry is not always possible owing to differences in chemical reactivity among the metals. Here we report a novel process to grow metal-oxide films in large areas at low cost using polymer-assisted deposition (PAD), where the polymer controls the viscosity and binds metal ions, resulting in a homogeneous distribution of metal precursors in the solution and the formation of uniform metal-organic films. The latter feature makes it possible to grow simple and complex crack-free epitaxial metal-oxides.

  3. Atmospheric corrosion and chloride deposition on metal surfaces

    SciTech Connect

    Matthes, Steven A.; Holcomb, Gordon R.; Cramer, Stephen D.; Covino, Bernard S., Jr.; Bullard, Sophie J.

    2004-01-01

    Atmospheric corrosion and chloride deposition on metal surfaces was studied at an unpolluted coastal (marine) site, an unpolluted rural inland site, and a polluted urban site. Chloride deposition by both wet (precipitation) and dry deposition processes over a multi-year period was measured using ion chromatography analysis of incident precipitation and precipitation runoff from the surface of metal samples. Chloride deposition was measured on zinc, copper, lead, mild steel, and non-reactive blank panels, as well as two panels coated with thermal-sprayed zinc alloys. Chloride deposition measured by runoff chemistry was compared with chloride deposition measurements made by the ASTM wet candle technique. Corrosion mass loss as a function of distance from the ocean is presented for copper and mild steel in bold exposures on the west coast.

  4. Electron Beam Freeform Fabrication: A Rapid Metal Deposition Process

    NASA Technical Reports Server (NTRS)

    Taminger, Karen M. B.; Hafley, Robert A.

    2003-01-01

    Manufacturing of structural metal parts directly from computer aided design (CAD) data has been investigated by numerous researchers over the past decade. Researchers at NASA Langley REsearch Center are developing a new solid freeform fabrication process, electron beam freeform fabrication (EBF), as a rapid metal deposition process that works efficiently with a variety of weldable alloys. The EBF process introduces metal wire feedstock into a molten pool that is created and sustained using a focused electron beam in a vacuum environment. Thus far, this technique has been demonstrated on aluminum and titanium alloys of interest for aerospace structural applications nickel and ferrous based alloys are also planned. Deposits resulting from 2219 aluminum demonstrations have exhibited a range of grain morphologies depending upon the deposition parameters. These materials ave exhibited excellent tensile properties comparable to typical handbook data for wrought plate product after post-processing heat treatments. The EBF process is capable of bulk metal deposition at deposition rated in excess of 2500 cubic centimeters per hour (150 cubic inches per our) or finer detail at lower deposition rates, depending upon the desired application. This process offers the potential for rapidly adding structural details to simpler cast or forged structures rather than the conventional approach of machining large volumes of chips to produce a monolithic metallic structure. Selective addition of metal onto simpler blanks of material can have a significant effect on lead time reduction and lower material and machining costs.

  5. Electroless metallization onto pulsed plasma deposited poly(4-vinylpyridine) surfaces.

    PubMed

    Bradley, T J; Schofield, W C E; Garrod, R P; Badyal, J P S

    2006-08-29

    Pulsed plasma-chemical deposition of poly(4-vinylpyridine) is found to be a highly effective way of functionalizing solid surfaces with pyridine ring centers. These surfaces can be metallized via complexation to Pd2+ ions from solution, followed by autocatalytic electroless deposition of either copper or nickel films.

  6. Star Clusters in M31. VII. Global Kinematics and Metallicity Subpopulations of the Globular Clusters

    NASA Astrophysics Data System (ADS)

    Caldwell, Nelson; Romanowsky, Aaron J.

    2016-06-01

    We carry out a joint spatial-kinematical-metallicity analysis of globular clusters (GCs) around the Andromeda Galaxy (M31), using a homogeneous, high-quality spectroscopic data set. In particular, we remove the contaminating young clusters that have plagued many previous analyses. We find that the clusters can be divided into three major metallicity groups based on their radial distributions: (1) an inner metal-rich group ([Fe/H] > -0.4); (2) a group with intermediate metallicity (with median [Fe/H] = -1) and (3) a metal-poor group, with [Fe/H] < -1.5. The metal-rich group has kinematics and spatial properties like those of the disk of M31, while the two more metal-poor groups show mild prograde rotation overall, with larger dispersions—in contrast to previous claims of stronger rotation. The metal-poor GCs are the least concentrated group; such clusters occur five times less frequently in the central bulge than do clusters of higher metallicity. Despite some well-known differences between the M31 and Milky Way GC systems, our revised analysis points to remarkable similarities in their chemodynamical properties, which could help elucidate the different formation stages of galaxies and their GCs. In particular, the M31 results motivate further exploration of a metal-rich GC formation mode in situ, within high-redshift, clumpy galactic disks.

  7. Interaction of hydrogen with palladium clusters deposited on graphene

    SciTech Connect

    Alonso, Julio A.; Granja, Alejandra; Cabria, Iván; López, María J.

    2015-12-31

    Hydrogen adsorption on nanoporous carbon materials is a promising technology for hydrogen storage. However, pure carbon materials do not meet the technological requirements due to the week binding of hydrogen to the pore walls. Experimental work has shown that doping with Pd atoms and clusters enhances the storage capacity of porous carbons. Therefore, we have investigated the role played by the Pd dopant on the enhancement mechanisms. By performing density functional calculations, we have found that hydrogen adsorbs on Pd clusters deposited on graphene following two channels, molecular adsorption and dissociative chemisorption. However, desorption of Pd-H complexes competes with desorption of hydrogen, and consequently desorption of Pd-H complexes would spoil the beneficial effect of the dopant. As a way to overcome this difficulty, Pd atoms and clusters can be anchored to defects of the graphene layer, like graphene vacancies. The competition between molecular adsorption and dissociative chemisorption of H{sub 2} on Pd{sub 6} anchored on a graphene vacancy has been studied in detail.

  8. Argon trapping in the depositing metal coating

    NASA Astrophysics Data System (ADS)

    Begrambekov, L. B.; Grunin, A. V.; Sadovskiy, Ya A.; Puntakov, N. A.; Utkov, N. S.; Zaharov, A. M.

    2017-05-01

    The paper has investigated conditions and parameters of argon trapping in molybdenum, tantalum and tungsten layers during their deposition on tungsten substrate by the atoms sputtered from the respective targets in argon plasma. The substrate temperature during deposition was 1273 K. The rate of deposition was 1 μm/h. It was shown that electron irradiation of the deposited layer with the beam intensity of 4 mA/cm2 initiated argon trapping in tungsten and tantalum coating with approx. 2 x 1027 at/m3 and 8 x 1026 at/cm3, respectively, but did not stimulate argon trapping in the molybdenum layers. Features of argon trapping in the tungsten coating and its release are investigated in detail.

  9. Spontaneous metal deposition from organic solutions for electronic materials applications

    NASA Astrophysics Data System (ADS)

    Fang, Rui

    Electrochemical deposition (ECD) has been used widely in the electronics industry. A novel "galvanic deposition" process was used for spontaneous and selective ECD of metal from organic solutions in contrast to the more conventional aqueous media. The more noble metal ions loaded in the organic solution are reduced and deposited onto the less noble metal substrate, which is simultaneously dissolved into the organic. Cu and Pd seed layers have been successfully deposited from organic solutions onto patterned and unpatterned pure aluminum and Al(0.5wt%Cu) thin films using this immersion displacement process. The Cu and Pd deposits were effectively used as catalytic sites for subsequent conventional electroless or electrolytic copper deposition. Further studies were performed to modify and optimize the organic deposition solution composition. These modified organic solutions could be used to deposit nearly continuous copper films on both unpatterned and patterned aluminum substrates. A patent disclosure on the modified organic deposition process was made to the University of Missouri and will be officially filed with the U.S. Patent Office. The EIS technique was one method used to characterize these high resistivity organic media. The organic solution resistivities were determined to be in the range of ˜108 O-cm but decreased to ˜10 6 O-cm with the addition of some modifying additives. Pd and Cu deposition have also been accomplished on various blanket and patterned Ti, TiN, Ta, and TaN barrier films. Some pre-treatment or in-situ etching in combination with ultrasonic or intensive mechanical agitation was necessary to activate the surface and enhance the metal deposition reaction. After seeding, continuous copper films were built up using a conventional electroless or electroplating process.

  10. Structure of overheated metal clusters: MD simulation study

    SciTech Connect

    Vorontsov, Alexander

    2015-08-17

    The structure of overheated metal clusters appeared in condensation process was studied by computer simulation techniques. It was found that clusters with size larger than several tens of atoms have three layers: core part, intermediate dense packing layer and a gas- like shell with low density. The change of the size and structure of these layers with the variation of internal energy and the size of cluster is discussed.

  11. Metal-Vapor Deposition Modulation on Soft Polymer Surfaces

    NASA Astrophysics Data System (ADS)

    Tsujioka, Tsuyoshi; Tsuji, Kosuke

    2012-02-01

    Metal-vapor deposition modulation on soft polymer surfaces and its applications are reported. A soft viscous surface of poly(dimethylsiloxane) (PDMS) with a glass transition temperature (Tg) of -123 °C showed perfect desorption at room temperature for many kinds of metal vapor. Metal-vapor deposition modulation on PDMS surfaces was applied to the Ca-cathode patterning of an organic light-emitting device, the preparation of thin-film Pb fuse, and the Mg vapor transportation by a pipeline, indicating great potential in various fields of basic research, engineering, and industry.

  12. Infrared Multiple Photon Dissociation Spectroscopy Of Metal Cluster-Adducts

    NASA Astrophysics Data System (ADS)

    Cox, D. M.; Kaldor, A.; Zakin, M. R.

    1987-01-01

    Recent development of the laser vaporization technique combined with mass-selective detection has made possible new studies of the fundamental chemical and physical properties of unsupported transition metal clusters as a function of the number of constituent atoms. A variety of experimental techniques have been developed in our laboratory to measure ionization threshold energies, magnetic moments, and gas phase reactivity of clusters. However, studies have so far been unable to determine the cluster structure or the chemical state of chemisorbed species on gas phase clusters. The application of infrared multiple photon dissociation IRMPD to obtain the IR absorption properties of metal cluster-adsorbate species in a molecular beam is described here. Specifically using a high power, pulsed CO2 laser as the infrared source, the IRMPD spectrum for methanol chemisorbed on small iron clusters is measured as a function of the number of both iron atoms and methanols in the complex for different methanol isotopes. Both the feasibility and potential utility of IRMPD for characterizing metal cluster-adsorbate interactions are demonstrated. The method is generally applicable to any cluster or cluster-adsorbate system dependent only upon the availability of appropriate high power infrared sources.

  13. Extraction of heavy metals characteristics of the 2011 Tohoku tsunami deposits using multiple classification analysis.

    PubMed

    Nakamura, Kengo; Kuwatani, Tatsu; Kawabe, Yoshishige; Komai, Takeshi

    2016-02-01

    Tsunami deposits accumulated on the Tohoku coastal area in Japan due to the impact of the Tohoku-oki earthquake. In the study reported in this paper, we applied principal component analysis (PCA) and cluster analysis (CA) to determine the concentrations of heavy metals in tsunami deposits that had been diluted with water or digested using 1 M HCl. The results suggest that the environmental risk is relatively low, evidenced by the following geometric mean concentrations: Pb, 16 mg kg(-1) and 0.003 ml L(-1); As, 1.8 mg kg(-1) and 0.004 ml L(-1); and Cd, 0.17 mg kg(-1) and 0.0001 ml L(-1). CA was performed after outliers were excluded using PCA. The analysis grouped the concentrations of heavy metals for leaching in water and acid. For the acid case, the first cluster contained Ni, Fe, Cd, Cu, Al, Cr, Zn, and Mn; while the second contained Pb, Sb, As, and Mo. For water, the first cluster contained Ni, Fe, Al, and Cr; and the second cluster contained Mo, Sb, As, Cu, Zn, Pb, and Mn. Statistical analysis revealed that the typical toxic elements, As, Pb, and Cd have steady correlations for acid leaching but are relatively sparse for water leaching. Pb and As from the tsunami deposits seemed to reveal a kind of redox elution mechanism using 1 M HCl. Copyright © 2015 The Authors. Published by Elsevier Ltd.. All rights reserved.

  14. EXPLORATION STRATEGY FOR HOT-SPRING PRECIOUS-METAL DEPOSITS.

    USGS Publications Warehouse

    Berger, Byron R.; Adams, Samuel S.

    1984-01-01

    The discovery of economic precious-metal deposits related to physical-chemical processes in the near-surface portions of high-temperature hot-spring systems has led to intensive exploration efforts for this deposit type. To increase the probability of success, these exploration programs should (1) be based on the most important visually recognizable or readily measurable deposit-model criteria; (2) be able to identify specific targets within the best search areas; and (3) be able to rank the order of priority among the targets. We propose a process-recognition exploration strategy for hot-spring deposits that has been developed from data from precious-metal occurrences at several localities in the western United States. The exploration model is based on the degree to which recognizable geologic and geochemical criteria are favorable or unfavorable to the occurrence of an economic deposit, either through their presence or absence.

  15. Plasma sprayed and electrospark deposited zirconium metal diffusion barrier coatings

    SciTech Connect

    Hollis, Kendall J; Pena, Maria I

    2010-01-01

    Zirconium metal coatings applied by plasma spraying and electrospark deposition (ESD) have been investigated for use as diffusion barrier coatings on low enrichment uranium fuel for research nuclear reactors. The coatings have been applied to both stainless steel as a surrogate and to simulated nuclear fuel uranium-molybdenum alloy substrates. Deposition parameter development accompanied by coating characterization has been performed. The structure of the plasma sprayed coating was shown to vary with transferred arc current during deposition. The structure of ESD coatings was shown to vary with the capacitance of the deposition equipment.

  16. SEDIMENT-HOSTED PRECIOUS METAL DEPOSITS.

    USGS Publications Warehouse

    Bagby, W.C.; Pickthorn, W.J.; Goldfarb, R.; Hill, R.A.

    1984-01-01

    The Dee mine is a sediment-hosted, disseminated gold deposit in the Roberts Mountains allochthon of north central Nevada. Soil samples were collected from the C-horizon in undisturbed areas over the deposit in order to investigate the usefulness of soil geochemistry in identifying this type of deposit. Each sample was sieved to minus 80 mesh and analyzed quantitatively for Au, Ag, As, Sb, Hg, Tl and semi-quantitative data for an additional 31 elements. Rank sum analysis is successful for the Au, Ag, As, Sb, Hg, Tl suite, even though bedrock geology is disregarded. This method involves data transformation into a total element signature by ranking the data in ascending order and summing the element ranks for each sample. The rank sums are then divided into percentile groups and plotted. The rank sum plot for the Dee soils unequivocally identifies three of four known ore zones.

  17. Influence of hydrofluoric acid treatment on electroless deposition of Au clusters.

    PubMed

    Milazzo, Rachela G; Mio, Antonio M; D'Arrigo, Giuseppe; Smecca, Emanuele; Alberti, Alessandra; Fisichella, Gabriele; Giannazzo, Filippo; Spinella, Corrado; Rimini, Emanuele

    2017-01-01

    The morphology of gold nanoparticles (AuNPs) deposited on a (100) silicon wafer by simple immersion in a solution containing a metal salt and hydrofluoric acid (HF) is altered by HF treatment both before and after deposition. The gold clusters are characterized by the presence of flat regions and quasispherical particles consistent with the layer-by-layer or island growth modes, respectively. The cleaning procedure, including HF immersion prior to deposition, affects the predominantly occurring gold structures. Flat regions, which are of a few tens of nanometers long, are present after immersion for 10 s. The three-dimensional (3D) clusters are formed after a cleaning procedure of 4 min, which results in a large amount of spherical particles with a diameter of ≈15 nm and in a small percentage of residual square layers of a few nanometers in length. The samples were also treated with HF after the deposition and we found out a general thickening of flat regions, as revealed by TEM and AFM analysis. This result is in contrast to the coalescence observed in similar experiments performed with Ag. It is suggested that the HF dissolves the silicon oxide layer formed on top of the thin flat clusters and promotes the partial atomic rearrangement of the layered gold atoms, driven by a reduction of the surface energy. The X-ray diffraction investigation indicated changes in the crystalline orientation of the flat regions, which partially lose their initially heteroepitaxial relationship with the substrate. A postdeposition HF treatment for almost 70 s has nearly the same effect of long duration, high temperature annealing. The process presented herein could be beneficial to change the spectral response of nanoparticle arrays and to improve the conversion efficiency of hybrid photovoltaic devices.

  18. Influence of hydrofluoric acid treatment on electroless deposition of Au clusters

    PubMed Central

    Mio, Antonio M; D’Arrigo, Giuseppe; Smecca, Emanuele; Alberti, Alessandra; Fisichella, Gabriele; Giannazzo, Filippo; Spinella, Corrado; Rimini, Emanuele

    2017-01-01

    The morphology of gold nanoparticles (AuNPs) deposited on a (100) silicon wafer by simple immersion in a solution containing a metal salt and hydrofluoric acid (HF) is altered by HF treatment both before and after deposition. The gold clusters are characterized by the presence of flat regions and quasispherical particles consistent with the layer-by-layer or island growth modes, respectively. The cleaning procedure, including HF immersion prior to deposition, affects the predominantly occurring gold structures. Flat regions, which are of a few tens of nanometers long, are present after immersion for 10 s. The three-dimensional (3D) clusters are formed after a cleaning procedure of 4 min, which results in a large amount of spherical particles with a diameter of ≈15 nm and in a small percentage of residual square layers of a few nanometers in length. The samples were also treated with HF after the deposition and we found out a general thickening of flat regions, as revealed by TEM and AFM analysis. This result is in contrast to the coalescence observed in similar experiments performed with Ag. It is suggested that the HF dissolves the silicon oxide layer formed on top of the thin flat clusters and promotes the partial atomic rearrangement of the layered gold atoms, driven by a reduction of the surface energy. The X-ray diffraction investigation indicated changes in the crystalline orientation of the flat regions, which partially lose their initially heteroepitaxial relationship with the substrate. A postdeposition HF treatment for almost 70 s has nearly the same effect of long duration, high temperature annealing. The process presented herein could be beneficial to change the spectral response of nanoparticle arrays and to improve the conversion efficiency of hybrid photovoltaic devices. PMID:28243555

  19. Removing Cool Cores and Central Metallicity Peaks in Galaxy Clusters with Powerful Active Galactic Nucleus Outbursts

    NASA Astrophysics Data System (ADS)

    Guo, Fulai; Mathews, William G.

    2010-07-01

    Recent X-ray observations of galaxy clusters suggest that cluster populations are bimodally distributed according to central gas entropy and are separated into two distinct classes: cool core (CC) and non-cool core (NCC) clusters. While it is widely accepted that active galactic nucleus (AGN) feedback plays a key role in offsetting radiative losses and maintaining many clusters in the CC state, the origin of NCC clusters is much less clear. At the same time, a handful of extremely powerful AGN outbursts have recently been detected in clusters, with a total energy ~1061-1062 erg. Using two-dimensional hydrodynamic simulations, we show that if a large fraction of this energy is deposited near the centers of CC clusters, which is likely common due to dense cores, these AGN outbursts can completely remove CCs, transforming them to NCC clusters. Our model also has interesting implications for cluster abundance profiles, which usually show a central peak in CC systems. Our calculations indicate that during the CC to NCC transformation, AGN outbursts efficiently mix metals in cluster central regions and may even remove central abundance peaks if they are not broad enough. For CC clusters with broad central abundance peaks, AGN outbursts decrease peak abundances, but cannot effectively destroy the peaks. Our model may simultaneously explain the contradictory (possibly bimodal) results of abundance profiles in NCC clusters, some of which are nearly flat, while others have strong central peaks similar to those in CC clusters. A statistical analysis of the sizes of central abundance peaks and their redshift evolution may shed interesting insights on the origin of both types of NCC clusters and the evolution history of thermodynamics and AGN activity in clusters.

  20. REMOVING COOL CORES AND CENTRAL METALLICITY PEAKS IN GALAXY CLUSTERS WITH POWERFUL ACTIVE GALACTIC NUCLEUS OUTBURSTS

    SciTech Connect

    Guo Fulai; Mathews, William G.

    2010-07-10

    Recent X-ray observations of galaxy clusters suggest that cluster populations are bimodally distributed according to central gas entropy and are separated into two distinct classes: cool core (CC) and non-cool core (NCC) clusters. While it is widely accepted that active galactic nucleus (AGN) feedback plays a key role in offsetting radiative losses and maintaining many clusters in the CC state, the origin of NCC clusters is much less clear. At the same time, a handful of extremely powerful AGN outbursts have recently been detected in clusters, with a total energy {approx}10{sup 61}-10{sup 62} erg. Using two-dimensional hydrodynamic simulations, we show that if a large fraction of this energy is deposited near the centers of CC clusters, which is likely common due to dense cores, these AGN outbursts can completely remove CCs, transforming them to NCC clusters. Our model also has interesting implications for cluster abundance profiles, which usually show a central peak in CC systems. Our calculations indicate that during the CC to NCC transformation, AGN outbursts efficiently mix metals in cluster central regions and may even remove central abundance peaks if they are not broad enough. For CC clusters with broad central abundance peaks, AGN outbursts decrease peak abundances, but cannot effectively destroy the peaks. Our model may simultaneously explain the contradictory (possibly bimodal) results of abundance profiles in NCC clusters, some of which are nearly flat, while others have strong central peaks similar to those in CC clusters. A statistical analysis of the sizes of central abundance peaks and their redshift evolution may shed interesting insights on the origin of both types of NCC clusters and the evolution history of thermodynamics and AGN activity in clusters.

  1. Miniemulsion synthesis of metal-oxo cluster containing copolymer nanobeads.

    PubMed

    Pablico, Michele H; Mertzman, Julie E; Japp, Emily A; Boncher, William L; Nishida, Maki; Van Keuren, Edward; Lofland, Samuel E; Dollahon, Norman; Rubinson, Judith F; Holman, K Travis; Stoll, Sarah L

    2011-10-18

    Hybrid nanobeads containing either a manganese-oxo or manganese-iron-oxo cluster have been prepared via the miniemulsion polymerization technique. Two new ligand substituted oxo clusters, Mn(12)O(12)(VBA)(16)(H(2)O)(4) and Mn(8)Fe(4)O(12)(VBA)(16)(H(2)O)(4) (where VBA = 4-vinylbenzoate), have been prepared and characterized. Polymerization of the functionalized metal-oxo clusters with styrene under miniemulsion conditions produced monodispersed polymer nanoparticles as small as ~60 nm in diameter. The metal-oxo polymer nanobeads were fully characterized in terms of synthetic parameters, composition, structure, and magnetic properties. © 2011 American Chemical Society

  2. Magnetic properties of supported metal atoms and clusters

    NASA Astrophysics Data System (ADS)

    Martins, Michael; Wurth, Wilfried

    2016-12-01

    Clusters are small systems ranging from a few atoms up to several thousand atoms. They are of high interest in basic research, but also for applications due to their specific electronic, magnetic or chemical properties depending on size and composition. For small clusters, quantum size effects play an important role and specific material properties might be tailored by choosing a special size or composition of the cluster. Here, we review the magnetic properties of adatoms and supported small mass-selected transition-metal clusters in the few-atom limit investigated by x-ray magnetic circular dichroism spectroscopy in the soft x-ray regime. The influence of cluster size, composition, the cluster-surface and intra-cluster interaction on the spin and orbital magnetic moments will be discussed.

  3. A new experimental setup for high-pressure catalytic activity measurements on surface deposited mass-selected Pt clusters

    SciTech Connect

    Watanabe, Yoshihide; Isomura, Noritake

    2009-09-15

    A new experimental setup to study catalytic and electronic properties of size-selected clusters on metal oxide substrates from the viewpoint of cluster-support interaction and to formulate a method for the development of heterogeneous catalysts such as automotive exhaust catalysts has been developed. The apparatus consists of a size-selected cluster source, a photoemission spectrometer, a scanning tunneling microscope (STM), and a high-pressure reaction cell. The high-pressure reaction cell measurements provided information on catalytic properties in conditions close to practical use. The authors investigated size-selected platinum clusters deposited on a TiO{sub 2}(110) surface using a reaction cell and STM. Catalytic activity measurements showed that the catalytic activities have a cluster-size dependency.

  4. Probing Globular Cluster Formation in Low Metallicity Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Johnson, Kelsey E.; Hunt, Leslie K.; Reines, Amy E.

    2008-12-01

    The ubiquitous presence of globular clusters around massive galaxies today suggests that these extreme star clusters must have been formed prolifically in the earlier universe in low-metallicity galaxies. Numerous adolescent and massive star clusters are already known to be present in a variety of galaxies in the local universe; however most of these systems have metallicities of 12 + log(O/H) > 8, and are thus not representative of the galaxies in which today's ancient globular clusters were formed. In order to better understand the formation and evolution of these massive clusters in environments with few heavy elements, we have targeted several low-metallicity dwarf galaxies with radio observations, searching for newly-formed massive star clusters still embedded in their birth material. The galaxies in this initial study are HS 0822+3542, UGC 4483, Pox 186, and SBS 0335-052, all of which have metallicities of 12 + log(O/H) < 7.75. While no thermal radio sources, indicative of natal massive star clusters, are found in three of the four galaxies, SBS 0335-052 hosts two such objects, which are incredibly luminous. The radio spectral energy distributions of these intense star-forming regions in SBS 0335-052 suggest the presence of ~12,000 equivalent O-type stars, and the implied star formation rate is nearing the maximum starburst intensity limit.

  5. GISAXS studies of model nanocatalysts synthesized by atomic cluster deposition.

    SciTech Connect

    Vajda, S.; Winans, R. E.; Ballentine, G. E.; Elam, J. W.; Lee, B.; Pellin, M. J.; Seifert, S.; Tikhonov, G. Y.; Tomczyk, N. A.

    2006-01-01

    Small nanoparticles possess unique, strongly size-dependent chemical and physical properties that make these particles ideal candidates for a number of applications, including catalysts or sensors due to their significantly higher activity and selectivity than their more bulk-like analogs. In the smallest size regime, nanocluster catalytic activity changes by orders of magnitude with the addition or removal of a single atom, thus allowing a tuning of the properties of these particles atom by atom. Equally effective tuning knobs for these model catalysts are the composition and morphology of the support, which can dramatically change the electronic structure of these particles, leading to drastic changes in both activity and specificity. However, the Achilles heal of these particles remains their sintering at elevated temperatures or when exposed to mixtures of reactive gases. In the presented paper, the issues of thermal stability, isomerization and growth of models of catalytic active sites - atomic gold and platinum clusters and nanoparticles produced by cluster deposition on technologically relevan oxide surfaces - is addressed by employing synchrotron X-ray radiation techniques.

  6. Properties and Chemisorptive Reactivity of Transition Metal Clusters

    DTIC Science & Technology

    1991-12-14

    structure of metal complexes that go beyond ligand field theory ideas, and of practical importance, in that it is crucial to understand how magnetic...aggregates or clusters of these metals with quntum mechanics, we will be able to develop a detailed understanding of metallic bonding. So far, we have...interactions between early and late TM’s in these so-called Engel-Brewer intermetallic compounds. The only theory that has attempted to explain the high

  7. UV laser deposition of metal films by photogenerated free radicals

    NASA Technical Reports Server (NTRS)

    Montgomery, R. K.; Mantei, T. D.

    1986-01-01

    A novel photochemical method for liquid-phase deposition of metal films is described. In the liquid phase deposition scheme, a metal containing compound and a metal-metal bonded carbonyl complex are dissolved together in a polar solvent and the mixture is irradiated using a UV laser. The optical arrangement consists of a HeCd laser which provides 7 mW of power at a wavelength of 325 nm in the TEM(OO) mode. The beam is attenuated and may be expanded to a diameter of 5-20 mm. Experiments with photochemical deposition of silver films onto glass and quartz substrates are described in detail. Mass spectrometric analysis of deposited silver films indicated a deposition rate of about 1 A/s at incident power levels of 0.01 W/sq cm. UV laser-induced copper and palladium films have also been obtained. A black and white photograph showing the silver Van Der Pauw pattern of a solution-deposited film is provided.

  8. Plasma assisted deposition of metal fluorides for 193nm applications

    NASA Astrophysics Data System (ADS)

    Bischoff, Martin; Sode, Maik; Gaebler, Dieter; Kaiser, Norbert; Tuennermann, Andreas

    2008-10-01

    The ArF lithography technology requires a minimization of optical losses due to scattering and absorption. Consequently it is necessary to optimize the coating process of metal fluorides. The properties of metal fluoride thin films are mainly affected by the deposition methods, their parameters, and the vacuum conditions. Until now the best results were achieved by metal boat evaporation with high substrate temperature and without plasma assistance. In fact, it was demonstrated that the plasma assisted deposition process results in optical thin films with high packing density but the losses due to absorption were extremely high for deep and vacuum ultraviolet applications. This paper will demonstrate that most of the common metal fluorides can be deposited by electron beam evaporation with plasma assistance. In comparison to other deposition methods, the prepared thin films show low absorption in the VUV spectral range, high packing density, and less water content. The densification of the thin films was performed by a Leybold LION plasma source. As working gas, a variable mixture of fluorine and argon gas was chosen. To understand the deposition process and the interaction of the plasma with the deposition material, various characterization methods like plasma emission spectroscopy and ion current measurements were implemented.

  9. UV laser deposition of metal films by photogenerated free radicals

    NASA Technical Reports Server (NTRS)

    Montgomery, R. K.; Mantei, T. D.

    1986-01-01

    A novel photochemical method for liquid-phase deposition of metal films is described. In the liquid phase deposition scheme, a metal containing compound and a metal-metal bonded carbonyl complex are dissolved together in a polar solvent and the mixture is irradiated using a UV laser. The optical arrangement consists of a HeCd laser which provides 7 mW of power at a wavelength of 325 nm in the TEM(OO) mode. The beam is attenuated and may be expanded to a diameter of 5-20 mm. Experiments with photochemical deposition of silver films onto glass and quartz substrates are described in detail. Mass spectrometric analysis of deposited silver films indicated a deposition rate of about 1 A/s at incident power levels of 0.01 W/sq cm. UV laser-induced copper and palladium films have also been obtained. A black and white photograph showing the silver Van Der Pauw pattern of a solution-deposited film is provided.

  10. Trinuclear Metal Clusters in Catalysis by Terpenoid Synthases

    PubMed Central

    Aaron, Julie A.; Christianson, David. W.

    2011-01-01

    Terpenoid synthases are ubiquitous enzymes that catalyze the formation of structurally and stereochemically diverse isoprenoid natural products. Many isoprenoid coupling enzymes and terpenoid cyclases from bacteria, fungi, protists, plants, and animals share the class I terpenoid synthase fold. Despite generally low amino acid sequence identity among these examples, class I terpenoid synthases contain conserved metal binding motifs that coordinate to a trinuclear metal cluster. This cluster not only serves to bind and orient the flexible isoprenoid substrate in the precatalytic Michaelis complex, but it also triggers the departure of the diphosphate leaving group to generate a carbocation that initiates catalysis. Additional conserved hydrogen bond donors assist the metal cluster in this function. Crystal structure analysis reveals that the constellation of three metal ions required for terpenoid synthase catalysis is generally identical among all class I terpenoid synthases of known structure. PMID:21562622

  11. Effect of Graphene with Nanopores on Metal Clusters

    SciTech Connect

    Zhou, Hu; Chen, Xianlang; Wang, Lei; Zhong, Xing; Zhuang, Guilin; Li, Xiaonian; Mei, Donghai; Wang, Jianguo

    2015-10-07

    Porous graphene, which is a novel type of defective graphene, shows excellent potential as a support material for metal clusters. In this work, the stability and electronic structures of metal clusters (Pd, Ir, Rh) supported on pristine graphene and graphene with different sizes of nanopore were investigated by first-principle density functional theory (DFT) calculations. Thereafter, CO adsorption and oxidation reaction on the Pd-graphene system were chosen to evaluate its catalytic performance. Graphene with nanopore can strongly stabilize the metal clusters and cause a substantial downshift of the d-band center of the metal clusters, thus decreasing CO adsorption. All binding energies, d-band centers, and adsorption energies show a linear change with the size of the nanopore: a bigger size of nanopore corresponds to a stronger metal clusters bond to the graphene, lower downshift of the d-band center, and weaker CO adsorption. By using a suitable size nanopore, supported Pd clusters on the graphene will have similar CO and O2 adsorption ability, thus leading to superior CO tolerance. The DFT calculated reaction energy barriers show that graphene with nanopore is a superior catalyst for CO oxidation reaction. These properties can play an important role in instructing graphene-supported metal catalyst preparation to prevent the diffusion or agglomeration of metal clusters and enhance catalytic performance. This work was supported by National Basic Research Program of China (973Program) (2013CB733501), the National Natural Science Foundation of China (NSFC-21176221, 21136001, 21101137, 21306169, and 91334013). D. Mei acknowledges the support from the US Department of Energy, Office of Science, Office of Basic Energy Sciences, Division of Chemical Sciences, Geosciences & Biosciences. Pacific Northwest National Laboratory (PNNL) is a multiprogram national laboratory operated for DOE by Battelle. Computing time was granted by the grand challenge of computational

  12. Aerosol chemical vapor deposition of metal oxide films

    DOEpatents

    Ott, Kevin C.; Kodas, Toivo T.

    1994-01-01

    A process of preparing a film of a multicomponent metal oxide including: forming an aerosol from a solution comprised of a suitable solvent and at least two precursor compounds capable of volatilizing at temperatures lower than the decomposition temperature of said precursor compounds; passing said aerosol in combination with a suitable oxygen-containing carrier gas into a heated zone, said heated zone having a temperature sufficient to evaporate the solvent and volatilize said precursor compounds; and passing said volatilized precursor compounds against the surface of a substrate, said substrate having a sufficient temperature to decompose said volatilized precursor compounds whereby metal atoms contained within said volatilized precursor compounds are deposited as a metal oxide film upon the substrate is disclosed. In addition, a coated article comprising a multicomponent metal oxide film conforming to the surface of a substrate selected from the group consisting of silicon, magnesium oxide, yttrium-stabilized zirconium oxide, sapphire, or lanthanum gallate, said multicomponent metal oxide film characterized as having a substantially uniform thickness upon said FIELD OF THE INVENTION The present invention relates to the field of film coating deposition techniques, and more particularly to the deposition of multicomponent metal oxide films by aerosol chemical vapor deposition. This invention is the result of a contract with the Department of Energy (Contract No. W-7405-ENG-36).

  13. Generation of metal-carbon and metal-nitrogen clusters with a laser induced plasma technique

    NASA Astrophysics Data System (ADS)

    Guo, B. C.; Wei, S.; Chen, Z.; Kerns, K. P.; Purnell, J.; Buzza, S.; Castleman, A. W., Jr.

    1992-10-01

    During the course of investigating dehydrogenation reactions induced by transition metals, we find that using a carrier gas containing hydrocarbons and ammonia instead of pure helium, in conjunction with a laser vaporization device, enables the facile production of metal-carbon and metal-nitrogen clusters in both the neutral and ionic forms. With only a change in the nature of the carrier gas, a variety of new classes of clusters can be produced.

  14. Inherent surface roughening as a limiting factor in epitaxial cluster deposition

    NASA Astrophysics Data System (ADS)

    Meinander, K.; Nordlund, K.; Keinonen, J.

    2005-01-01

    Deposition of nanoclusters at thermal energies will result in an onset of roughening of the deposited surface. In order to grow epitaxial films using cluster deposition at soft landing conditions, the effect of this inherent surface roughness on the alignment of deposited clusters must be investigated. Using molecular dynamics computer simulations we have determined the maximum size of Cu clusters that will align epitaxially, upon deposition at thermal energies, on rough (1 0 0) Cu substrates with temperatures ranging from 0 K to 750 K. We have also shown that the likelihood of epitaxial alignment for the resulting structures is dependent on the point of impact of a cluster relative to previously deposited clusters.

  15. Vacuum metal deposition: factors affecting normal and reverse development of latent fingerprints on polyethylene substrates.

    PubMed

    Jones, N; Stoilovic, M; Lennard, C; Roux, C

    2001-01-01

    Vacuum metal deposition (VMD) is an established technique for the development of latent fingerprints on non-porous surfaces. VMD has advantages over cyanoacrylate fuming, especially in circumstances where prints are old, have been exposed to adverse environmental conditions, or are present on semi-porous surfaces. Under normal circumstances, VMD produces 'negative' prints as zinc deposits onto the background substrate and not the print ridges themselves. A phenomenon of 'reverse' development, when zinc deposits onto the print ridges and not the background, has been reported by many authors but its causes have not been conclusively identified. Four plastic substrates were used in this study and these could be easily divided into two groups based on the types of development observed as the amount of deposited gold was increased. On group I plastics, identified as low-density polyethylene (LDPE), normal development then reverse development and finally no development resulted with increasing gold. On group II plastics, identified as high-density polyethylene (HDPE), normal development then over-development and finally poor-quality normal development resulted with increasing gold. Our results suggest that the difference between these plastic types causes variations in the gold film structure which in turn dictates the nature of the zinc deposition. On group I plastics, the structure and thickness of the gold film has been identified as the critical factor in the occurrence of normal or reverse development. Thin gold films on plastic substrates form small 'clusters' (or agglomerates) rather than the atoms being uniformly spread over the surface. The size and shape of these clusters is critical. Once the clusters reach a certain morphology, they no longer act as nucleation sites for zinc, and hence, zinc will not deposit onto the substrate. On group II plastics, results suggest that the gold clusters are smaller and more densely packed. Hence, even though the same amount

  16. Metallic clusters on a model surface: Quantum versus geometric effects

    NASA Astrophysics Data System (ADS)

    Blundell, S. A.; Haldar, Soumyajyoti; Kanhere, D. G.

    2011-08-01

    We determine the structure and melting behavior of supported metallic clusters using an ab initio density-functional-based treatment of intracluster interactions and an approximate treatment of the surface as an idealized smooth plane yielding an effective Lennard-Jones interaction with the ions of the cluster. We apply this model to determine the structure of sodium clusters containing from 4 to 22 atoms, treating the cluster-surface interaction strength as a variable parameter. For a strong cluster-surface interaction, the clusters form two-dimensional (2D) monolayer structures; comparisons with calculations of structure and dissociation energy performed with a classical Gupta interatomic potential show clearly the role of quantum shell effects in the metallic binding in this case, and evidence is presented that these shell effects correspond to those for a confined 2D electron gas. The thermodynamics and melting behavior of a supported Na20 cluster is considered in detail using the model for several cluster-surface interaction strengths. We find quantitative differences in the melting temperatures and caloric curve from density-functional and Gupta treatments of the valence electrons. A clear dimensional effect on the melting behavior is also demonstrated, with 2D structures showing melting temperatures above those of the bulk or (at very strong cluster-surface interactions) no clear meltinglike transition.

  17. Metal Organic-Chemical Vapor Deposition fabrication of semiconductor lasers

    NASA Astrophysics Data System (ADS)

    Thomas, C.

    1980-08-01

    The metal organic chemical vapor deposition (MO-CVD) process was studied and implemented in detail. Single crystal GaAs, and Ga(x)Al(1-x)As films were grown on GaAs by depositing metal organic alkyl gallium compounds in the presence of an arsine mixture. The metal organic chemical vapor deposition process allowed formation of the semiconductor compound directly on the heated substrate in only one hot temperature zone. With MO-CVD, semiconductor films can be efficiently produced by a more economical, less complicated process which will lend itself more easily than past fabrication procedures, to high quantity, high quality reproduction techniques of semiconductor lasers. Clearly MO-CVD is of interest to the communication industry where semiconductor lasers are used extensively in fiber optic communication systems, and similarly to the solar energy business where GaAs substrates are used as photoelectric cells.

  18. Heavy metals contamination of soils surrounding waste deposits in Romania

    NASA Astrophysics Data System (ADS)

    Matache, M.; Rozylowicz, L.; Ropota, M.; Patroescu, C.

    2003-05-01

    Soils contamination with heavy metals is one of the most severe aspects of environmental pollution in Romania, independently of the origin sources (domestic or industrial activities) or type of disposal (organised landfill or hazardous deposits)[l-2]. This fact is the consequence of the poor state of the existing waste deposits in Romania and of the significant costs involved by the establishing of a new landfill according with the international regulations. The present study is trying to emphasise the contamination of soils surrounding different categories of waste deposits (sewage sludge ponds, domestic and industrial waste landfills, hillocks, sterile deposits) from various regions of Romania. Some case studies show a special interest being localise in a protected area (Iron Gates Natural Park). In order to quantify the concentration of metals like Cd, Cr, Cu, Pb, Zn, Ni, Mo in soil samples, analysis were performed using Inductively Coupled Plasma - Optical Emission Spectrometry (ICP-OES). Romanian standards were used as reference values[3].

  19. Characteristics of a direct metal ion beam deposition source

    NASA Astrophysics Data System (ADS)

    Kim, Daeil; Kim, Steven

    2002-07-01

    In this study, we examine the performance of a direct metal ion beam deposition (DMIBD) system which uses a Cs-mordenite pellet as the ion source. We describe design aspects of DMIBD and process parameters such as secondary ion yields, secondary ion energy distributions, secondary ion to atom arrival ratios and deposition rates for C, Al, Si, Ni, Cu, Ta, and W targets. During deposition, the secondary negative metal ion yield strongly depends on the primary Cs+ ion does and bombarding energy. Also, the deposition rate and ion to atom arrival ratios for various targets can be controlled by adjusting the primary Cs+ ion dose, Cs+ ion bombarding energy, and ion beam energy to fit the desired application. copyright 2002 American Vacuum Society.

  20. Probing Metal Cluster and Metal Oxide Cluster Interactions with Organo-Sulfur and Organo-Phosphorous Molecules using Mass Spectrometry and Anion PES

    DTIC Science & Technology

    2007-11-02

    DATES COVERED Final 01 Dec 02 – 30 Nov 03 4. TITLE AND SUBTITLE Probing metal cluster and metal oxide cluster interactions with organo -sulfur and... Organo -phosphorous molecules using mass spectrometry and anion PES 5. FUNDING NUMBERS DAAD19-03-1-0009 6. AUTHOR(S) Caroline...298-102 Probing metal cluster and metal oxide cluster interactions with organo -sulfur and organo

  1. Electronic charging of non-metallic clusters: size-selected Mo(x)S(y) clusters supported on an ultrathin alumina film on NiAl(110).

    PubMed

    Zhou, Jing; Zhou, Jia; Camillone, Nicholas; White, Michael G

    2012-06-14

    Two photon photoemission was used to investigate the interfacial charge transfer for size-selected Mo(x)S(y) (x/y: 2/6, 4/6, 6/8, 7/10) clusters deposited on an ultrathin alumina film prepared on a NiAl(110) surface. The local work function of the surface increases with increasing cluster coverage, which is unexpected for charge transfer resulting from the formation of Mo-O bonds between the clusters and the alumina surface. By analogy with Au atoms and clusters on metal-supported ultrathin oxide films, we invoke electron tunneling from the NiAl substrate to explain the charge transfer to the Mo(x)S(y) clusters. Electron tunneling is favored by the large electron affinities of the Mo(x)S(y) clusters and the relatively low work function induced by the presence of the alumina film. The interfacial dipole moments derived from coverage-dependent measurements are cluster dependent and reflect differences in Mo(x)S(y) cluster structure and surface bonding. These results extend previous observations of electronic charging to non-metallic clusters, specifically, metal sulfides, and suggest a novel way to modify the electronic structure and reactivity of nanocatalysts for heterogeneous chemistry.

  2. From atoms to layers: in situ gold cluster growth kinetics during sputter deposition

    NASA Astrophysics Data System (ADS)

    Schwartzkopf, Matthias; Buffet, Adeline; Körstgens, Volker; Metwalli, Ezzeldin; Schlage, Kai; Benecke, Gunthard; Perlich, Jan; Rawolle, Monika; Rothkirch, André; Heidmann, Berit; Herzog, Gerd; Müller-Buschbaum, Peter; Röhlsberger, Ralf; Gehrke, Rainer; Stribeck, Norbert; Roth, Stephan V.

    2013-05-01

    The adjustment of size-dependent catalytic, electrical and optical properties of gold cluster assemblies is a very significant issue in modern applied nanotechnology. We present a real-time investigation of the growth kinetics of gold nanostructures from small nuclei to a complete gold layer during magnetron sputter deposition with high time resolution by means of in situ microbeam grazing incidence small-angle X-ray scattering (μGISAXS). We specify the four-stage growth including their thresholds with sub-monolayer resolution and identify phase transitions monitored in Yoneda intensity as a material-specific characteristic. An innovative and flexible geometrical model enables the extraction of morphological real space parameters, such as cluster size and shape, correlation distance, layer porosity and surface coverage, directly from reciprocal space scattering data. This approach enables a large variety of future investigations of the influence of different process parameters on the thin metal film morphology. Furthermore, our study allows for deducing the wetting behavior of gold cluster films on solid substrates and provides a better understanding of the growth kinetics in general, which is essential for optimization of manufacturing parameters, saving energy and resources.The adjustment of size-dependent catalytic, electrical and optical properties of gold cluster assemblies is a very significant issue in modern applied nanotechnology. We present a real-time investigation of the growth kinetics of gold nanostructures from small nuclei to a complete gold layer during magnetron sputter deposition with high time resolution by means of in situ microbeam grazing incidence small-angle X-ray scattering (μGISAXS). We specify the four-stage growth including their thresholds with sub-monolayer resolution and identify phase transitions monitored in Yoneda intensity as a material-specific characteristic. An innovative and flexible geometrical model enables the extraction

  3. Chemiluminescence in the Agglomeration of Metal Clusters

    PubMed

    König; Rabin; Schulze; Ertl

    1996-11-22

    The agglomeration of copper or silver atoms in a matrix of noble gas atoms to form small clusters may be accompanied by the emission of visible light. Spectral analysis reveals the intermediate formation of electronically excited atoms and dimers as the source of the chemiluminescence. A mechanism is proposed, according to which the gain in binding energy upon cluster formation may even lead to the ejection of excited fragments as a result of unstable intermediate configurations. A similar concept was introduced in the field of nuclear reactions by Niels Bohr 60 years ago.

  4. Metallic Clusters in Strong Femtosecond Laser Pulses

    NASA Astrophysics Data System (ADS)

    Suraud, Eric; Reinhard, P.-G.; Ullrich, Carsten A.

    1998-03-01

    We present a theoretical study of the electron response of a Na_9^+ cluster excited by strong femtosecond laser pulses.(C. A. Ullrich, P.-G. Reinhard, and E. Suraud, J. Phys. B 30), 5043 (1997) Our approach is based on time-dependent density functional theory within the adiabatic local density approximation, including a recently developed self-interaction correction scheme. We investigate numerically the full electronic dipolar response and multiphoton ionization of the cluster and discuss the ionization mechanism. A strong correlation between induced electronic dipole oscillations and electron emission is observed, leading to a pronounced resonant enhancement of ionization at the frequency of the Mie plasmon.

  5. Applications of superatom theory in metal cluster chemistry

    NASA Astrophysics Data System (ADS)

    Tofanelli, Marcus A.

    One of the largest modern scientific debates is understanding the size dependent properties of a metal. While much effort has been performed on understanding metal particles from the top down to much less work has been accomplished from the bottom up. This has lead to a great deal of interest in metal clusters. Metal clusters containing 20 to 200 metal atoms are similar yet strikingly different to both to normal coordination chemistry and continuous bulk systems, therefore neither a classical understanding for bulk or molecular systems appears to be appropriate. Superatom theory has emerged as a useful concept for describing the properties of a metal cluster in this size range. In this model a new set of 'superatomic' orbitals arises from the valence electrons of all the metals in a cluster. From superatom theory the properties of a metal cluster, such as stability, ionization energy, reactivity, and magnetism, should depend on valence of the superatomic orbitals, similar to a normal atom. However superatom theory has largely been used to describe the high stabilities of metal clusters with completed electronic configurations. Thus many features of superatom theory have remained largely untested and the extent that the superatom model truly applies has remained in question for many years. Over the past decade increases in synthetic and analytical techniques have allowed for the isolation of a series of stable monodisperse gold thiolate monolayer protected clusters (MPCs) containing from 10 to 500 gold atoms. The wide range in sizes and high stability of gold thiolate clusters provides an instrumental system for understanding superatom theory and the transition from molecular-like cluster to bulk-like system. In the first part of this thesis the effects of the superatomic valence is investigated under superatomic assumptions. Au25(SR)18 (where SR= any thiolate) can be synthesized in 3 different oxidation states without any major distortions to the geometry of the

  6. ELECTROCATALYSIS ON SURFACES MODIFIED BY METAL MONOLAYERS DEPOSITED AT UNDERPOTENTIALS.

    SciTech Connect

    ADZIC,R.

    2000-12-01

    The remarkable catalytic properties of electrode surfaces modified by monolayer amounts of metal adatoms obtained by underpotential deposition (UPD) have been the subject of a large number of studies during the last couple of decades. This interest stems from the possibility of implementing strictly surface modifications of electrocatalysts in an elegant, well-controlled way, and these bi-metallic surfaces can serve as models for the design of new catalysts. In addition, some of these systems may have potential for practical applications. The UPD of metals, which in general involves the deposition of up to a monolayer of metal on a foreign substrate at potentials positive to the reversible thermodynamic potential, facilitates this type of surface modification, which can be performed repeatedly by potential control. Recent studies of these surfaces and their catalytic properties by new in situ surface structure sensitive techniques have greatly improved the understanding of these systems.

  7. METAL PRODUCTION IN GALAXY CLUSTERS: THE NON-GALACTIC COMPONENT

    SciTech Connect

    Bregman, Joel N.; Anderson, Michael E.; Dai Xinyu E-mail: michevan@umich.ed

    2010-06-10

    The metallicity in galaxy clusters is expected to originate from the stars in galaxies, with a population dominated by high-mass stars likely being the most important stellar component, especially in rich clusters. We examine the relationship between the metallicity and the prominence of galaxies as measured by the star-to-baryon ratio, M{sub *}/M{sub bary}. Counter to expectations, we rule out a metallicity that is proportional to M{sub *}/M{sub bary}, where the best fit has the gas-phase metallicity decreasing with M{sub *}/M{sub bary}, or the metallicity of the gas plus the stars being independent of M{sub *}/M{sub bary}. This implies that the population of stars responsible for the metals is largely proportional to the total baryonic mass of the cluster, not to the galaxy mass within the cluster. If generally applicable, most of the heavy elements in the universe were not produced within galaxies.

  8. Cluster variation study of the underpotential deposition of Cu on Au(111) in the presence of bisulfate

    NASA Astrophysics Data System (ADS)

    Huckaby, Dale A.; Legault, Marc D.; Blum, L.

    1998-09-01

    A cluster variation method is developed to study the phase transitions and the structures of phases which occur at the fluid-crystal interface during the underpotential deposition of a metal on an electrode in the presence of an anion, such as bisulfate. In addition to the possibility of first-order condensation phase transitions occurring during the deposition of a metal, the steric repulsion of adsorbed anions can also cause an order-disorder transition. Using clusters containing six adsorption sites, the method is applied to the underpotential deposition of copper on (111) gold in the presence of bisulfate. In order to fix a constant in the expression for the entropy, the effect of the hard-core exclusion of a pair of first-neighbor bisulfates, in addition to the effect of finite interactions, is calculated exactly in the limit of high temperature. The cluster method yields two coupled adsorption isotherms for copper and bisulfate in terms of their activities and coverages. The resulting isotherms show an order-disorder transition due to the hard-core exclusion of neighboring bisulfate ions, as well as two first-order phase transitions in the copper and bisulfate coverages which correspond to the two spikes in the experimental voltammogram. The cluster method also gives the local structure of the phases which occur as the voltage is changed.

  9. Systems and methods for producing metal clusters; functionalized surfaces; and droplets including solvated metal ions

    DOEpatents

    Cooks, Robert Graham; Li, Anyin; Luo, Qingjie

    2017-08-01

    The invention generally relates to systems and methods for producing metal clusters; functionalized surfaces; and droplets including solvated metal ions. In certain aspects, the invention provides methods that involve providing a metal and a solvent. The methods additionally involve applying voltage to the solvated metal to thereby produce solvent droplets including ions of the metal containing compound, and directing the solvent droplets including the metal ions to a target. In certain embodiments, once at the target, the metal ions can react directly or catalyze reactions.

  10. Systems and methods for producing metal clusters; functionalized surfaces; and droplets including solvated metal ions

    DOEpatents

    Cooks, Robert Graham; Li, Anyin; Luo, Qingjie

    2017-01-24

    The invention generally relates to systems and methods for producing metal clusters; functionalized surfaces; and droplets including solvated metal ions. In certain aspects, the invention provides methods that involve providing a metal and a solvent. The methods additionally involve applying voltage to the solvated metal to thereby produce solvent droplets including ions of the metal containing compound, and directing the solvent droplets including the metal ions to a target. In certain embodiments, once at the target, the metal ions can react directly or catalyze reactions.

  11. Ion-beam-assisted deposition of metal nanocluster thin films with nonlinear optical properties

    SciTech Connect

    Cotell, C.M.; Carosella, C.A.; Flom, S.R.; Schiestel, S.; Haralampus, N.; Barnett, T.W.; Bartoli, F.J.

    1996-12-31

    Metal nanocluster thin films ({approximately} 200 nm thickness) consisting of noble metal (Au) clusters (5--30 nm) in an active metal oxide (Nb{sub 2}O{sub 5}) matrix were deposited by evaporation or ion beam assisted deposition (IBAD). In some cases the films were given a post-deposition anneal. The microstructure of the films was examined by plan view and cross sectional transmission electron microscopy (TEM). The size of the metal nanoclusters was found to depend upon the temperature of the post-deposition anneal as well as the conditions of ion bombardment. Ion bombardment was found to stabilize smaller size particles. The linear optical properties of the films, as measured by VIS/UV spectroscopy, show particle size-dependent surface plasmon resonance effects. The nonlinear optical (NLO) properties of the nanoclusters in oxidized niobium were probed experimentally using degenerate four wave mixing (DFWM) and nonlinear transmission (NLT). The DFWM measurements yielded signals that showed strong evidence of saturation and give large values of {vert_bar}{chi}{sup (3)}{sub xxxx}{vert_bar}. NLT measurements demonstrated that the nonlinear absorption coefficient and, hence, I{sub m}{chi}{sup (3)}{sub xxxx} was negative. Time resolved DFWM measurements exhibited dynamics that decayed on a several picosecond time scale. The magnitude and the picosecond dynamics of the NLO response were compared to those observed in gold nanoclusters formed by ion implantation in other media. The advantages of the IBAD method for fabricating third order NLO films include the ability to deposit films of arbitrary active region thickness and, more importantly, high cluster densities.

  12. Electrochemically induced maskless metal deposition on micropore wall.

    PubMed

    Liu, Jie; Hébert, Clément; Pham, Pascale; Sauter-Starace, Fabien; Haguet, Vincent; Livache, Thierry; Mailley, Pascal

    2012-05-07

    By applying an external electric field across a micropore via an electrolyte, metal ions in the electrolyte can be reduced locally onto the inner wall of the micropore, which was fabricated in a silica-covered silicon membrane. This maskless metal deposition on the silica surface is a result of the pore membrane polarization in the electric field. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Synthesis and deposition of metal nanoparticles by gas condensation process

    SciTech Connect

    Maicu, Marina Glöß, Daniel; Frach, Peter; Schmittgens, Ralph; Gerlach, Gerald; Hecker, Dominic

    2014-03-15

    In this work, the synthesis of Pt and Ag nanoparticles by means of the inert gas phase condensation of sputtered atomic vapor is presented. The process parameters (power, sputtering time, and gas flow) were varied in order to study the relationship between deposition conditions and properties of the nanoparticles such as their quantity, size, and size distribution. Moreover, the gas phase condensation process can be combined with a plasma enhanced chemical vapor deposition procedure in order to deposit nanocomposite coatings consisting of metallic nanoparticles embedded in a thin film matrix material. Selected examples of application of the generated nanoparticles and nanocomposites are discussed.

  14. Corrosion processes of physical vapor deposition-coated metallic implants.

    PubMed

    Antunes, Renato Altobelli; de Oliveira, Mara Cristina Lopes

    2009-01-01

    Protecting metallic implants from the harsh environment of physiological fluids is essential to guaranteeing successful long-term use in a patient's body. Chemical degradation may lead to the failure of an implant device in two different ways. First, metal ions may cause inflammatory reactions in the tissues surrounding the implant and, in extreme cases, these reactions may inflict acute pain on the patient and lead to loosening of the device. Therefore, increasing wear strength is beneficial to the performance of the metallic implant. Second, localized corrosion processes contribute to the nucleation of fatigue cracks, and corrosion fatigue is the main reason for the mechanical failure of metallic implants. Common biomedical alloys such as stainless steel, cobalt-chrome alloys, and titanium alloys are prone to at least one of these problems. Vapor-deposited hard coatings act directly to improve corrosion, wear, and fatigue resistances of metallic materials. The effectiveness of the corrosion protection is strongly related to the structure of the physical vapor deposition layer. The aim of this paper is to present a comprehensive review of the correlation between the structure of physical vapor deposition layers and the corrosion properties of metallic implants.

  15. Nonlinear plasmon response in highly excited metallic clusters

    SciTech Connect

    Calvayrac, F.; Reinhard, P.G.; Suraud, E.

    1995-12-15

    We present a dynamical study of the electron response of metallic clusters in the nonlinear regime, as excited, e.g., in ion-cluster interactions or with intense laser beams. We use a quantal time-dependent local-density approximation in axial symmetry to describe the electron dynamics. Ions are either treated in a jellium approximation or explicitly. We find different dynamical regimes depending on the symmetries of the ionic background.

  16. Mechanism of deposit formation on fuel-wetted metal surfaces

    SciTech Connect

    Stavinoha, L.L.; Westbrook, S.R.; McInnis, L.A.

    1995-05-01

    Experiments were performed in a Single-Tube Heat Exchanger (STHE) apparatus and a Hot Liquid Process Simulator (HLPS) configured and operated to meet Jet Fuel Thermal Oxidation Tester (JFTOT) ASTM D 3241 requirements. The HLPS-JFTOT heater tubes used were 1018 mild steel, 316 stainless steel (SS), 304 stainless steel (SS), and 304 SS tubes coated with aluminum, magnesium, gold, and copper. A low-sulfur Jet A fuel with a breakpoint temperature of 254{degrees}C was used to create deposits on the heater tubes at temperatures of 300{degrees}C, 340{degrees}C, and 380{degrees}C. Deposit thickness was measured by dielectric breakdown voltage and Auger ion milling. Pronounced differences between the deposit thickness measuring techniques suggested that both the Auger milling rate and the dielectric strength of the deposit may be affected by deposit morphology/composition (such as metal ions that may have become included in the bulk of the deposit). Carbon burnoff data were obtained as a means of judging the validity of DMD-derived deposit evaluations. ESCA data suggest that the thinnest deposit was on the magnesium-coated test tube. The Scanning Electron Microscope (SEM) photographs showed marked variations in the deposit morphology and the results suggested that surface composition has a significant effect on the mechanism of deposition. The most dramatic effect observed was that the bulk of deposits moved to tube locations of lower temperature as the maximum temperature of the tube was increased from 300{degrees} to 380{degrees}C, also verified in a single-tube heat exchanger. The results indicate that the deposition rate and quantity at elevated temperatures is not completely temperature dependent, but is limited by the concentration of dissolved oxygen and/or reactive components in the fuel over a temperature range.

  17. The effect of alkylating agents on model supported metal clusters

    SciTech Connect

    Erdem-Senatalar, A.; Blackmond, D.G.; Wender, I. . Dept. of Chemical and Petroleum Engineering); Oukaci, R. )

    1988-01-01

    Interactions between model supported metal clusters and alkylating agents were studied in an effort to understand a novel chemical trapping technique developed for identifying species adsorbed on catalyst surfaces. It was found that these interactions are more complex than had previously been suggested. Studies were completed using deuterium-labeled dimethyl sulfate (DMS), (CH{sub 3}){sub 2}SO{sub 4}, as a trapping agent to interact with the supported metal cluster ethylidyne tricobalt enneacarbonyl. Results showed that oxygenated products formed during the trapping reaction contained {minus}OCD{sub 3} groups from the DMS, indicating that the interaction was not a simple alkylation. 18 refs., 1 fig., 3 tabs.

  18. Abundances for globular cluster giants. I. Homogeneous metallicities for 24 clusters

    NASA Astrophysics Data System (ADS)

    Carretta, E.; Gratton, R. G.

    1997-01-01

    We have obtained high resolution, high signal-to-noise ratio CCD echelle spectra of 10 bright red giants in 3 globular clusters (47 Tuc, NGC 6752 and NGC 6397) roughly spanning the whole range of metallicities of the galactic globular cluster system. The analysis of this newly acquired material reveals no significant evidence of star-to-star variation of the [Fe/H] ratio in these three clusters. Moreover, a large set of high quality literature data (equivalent widths from high dispersion CCD spectra) was re-analyzed in an homogeneous and self-consistent way to integrate our observations and derive new metal abundances for more than 160 bright red giants in 24 globular clusters (i.e. about 16% of the known population of galactic globulars). This set was then used to define a new metallicity scale for globular clusters which is the result of high quality, direct spectroscopic data, of new and updated model atmospheres from the grid of \\cite[Kurucz (1992)]{\\ref41}, and of a careful fine abundance analysis; this last, in turn, is based on a common set of both atomic and atmospheric parameters for all the stars examined. Given the very high degree of internal homogeneity, our new scale supersedes the offsets and discrepancies existing in previous attempts to obtain a metallicity scale. The internal uncertainty in [Fe/H] is very small: 0.06 dex (24 clusters) on average, and can be interpreted also as the mean precision of the c luster ranking. Compared to our system, metallicities on the widely used Zinn and West's scale are about 0.10 dex higher for [Fe/H]>-1, 0.23 dex lower for -1<[Fe/H]<-1.9 and 0.11 dex too high for [Fe/H]<-1.9. The non-linearity of the Zinn and West's scale is significant even at 3 sigma level. A quadratic transformation is given to correct older values to the new scale in the range of our calibrating clusters (-2.24 <= [Fe/H]ZW <= -0.51). A minor disagreement is found at low metallicities between the metallicity scale based on field and cluster

  19. Scattering of electrons on metal clusters and fullerenes

    NASA Astrophysics Data System (ADS)

    Gerchikov, Leonid G.; Solov'yov, Andrey V.; Connerade, Jean-Patrick; Greiner, Walter

    1997-09-01

    It is shown that the main contribution to the elastic cross section of fast electrons on metal clusters and fullerenes results from scattering on the frozen cluster potential, which is determined by the electron density distribution of the ground state of the target cluster. The specific shape of the electron distribution in fullerenes and metal clusters manifests itself in the diffraction behaviour of the elastic differential cross section. The analysis of the total elastic cross section dependence upon projectile velocity, the number of atoms in the cluster and its size is provided. The cross section of elastic scattering on a cluster surpasses the sum of the individual scattering cross sections on the equivalent number of isolated atoms. This occurs because of the coherent interaction of the projectile electron with electrons delocalized in the cluster volume. We have demonstrated that collective electron excitations sensitive to the many-electron correlations dominate inelastic scattering. The surface plasmon resonances can be observed in the differential cross section for inelastic scattering. We found a condition for the quadrupole and higher multipole plasmon excitations to contribute relatively little to the electron energy loss spectrum. The results obtained have been compared with experimental data for the electron - fullerene 0953-4075/30/18/013/img7 collision. Reasonable agreement between theoretical and experimental results is reported. We have also demonstrated that plasmon excitations provide the main contribution to the total inelastic cross section over a wide energy range. We have calculated the dependence of the total inelastic cross section on collision energy and compared the result obtained with the experimental data available, giving an interpretation for the plateau region in the cross section as caused by plasmon excitations rather than the cluster fragmentation process. We have shown that the single-particle jellium approximation fails to

  20. STEM characterization of metal clusters in/on oxides

    NASA Astrophysics Data System (ADS)

    Mehraeen, Shareghe

    Dispersed metal clusters in or on a support matrix are key phenomenons in many technological fields. Two widely used examples of them which are investigated in this thesis are supported-metal clusters in heterogeneous catalysis and transition metal clusters in diluted magnetic semiconductors (DMS) applied in spintronics. The catalytic activity and selectivity of catalysts often depend sensitively on structure parameters, such as particles size and shape. With the same analogy, the magnetic properties of DMS oxides are sensitively related to the crystal defects of the host material as a consequence of doping the transition metal. Therefore it is essential to develop and understand the correlation between nanostructure and function of these materials. STEM Z-contrast imaging is the best candidate for this type of study because of a high degree of resolution it provides and the unique ability it offers to detect and differentiate between the clusters and oxide matrix due to the large difference between their atomic numbers. Moreover the technique development in the STEM field fosters the conjugation of electron energy Loss Spectroscopy (EELS) and Z-contrast imaging and their widespread use for nearly atomic level chemical analysis at interface, second phases, and isolated defects. The advanced preparation method of supported clusters catalysts which is by carbonyl ligands offers a controlled cluster size and shape. MgO-supported Os clusters and SiO2-supported Ta clusters prepared by this method are adsorbed on oxide to convert into single-sized supported metal aggregates. The last step of preparation method is by removal of the ligands (decarbonylation) which is very important because it determines the final size distribution and shape of such clusters. Reaching carbonylated decaosmium clusters with the size of theoretically 0.295 nm and the tetrahedral-shape geometry are the aim of the preparation method. The size distribution measurements of sub-nanoclusters of

  1. Interaction of metallic clusters with biologically active curcumin molecules

    NASA Astrophysics Data System (ADS)

    Gupta, Sanjeev K.; He, Haiying; Liu, Chunhui; Dutta, Ranu; Pandey, Ravindra

    2015-09-01

    We have investigated the interaction of subnano metallic Gd and Au clusters with curcumin, an important biomolecule having pharmacological activity. Gd clusters show different site preference to curcumin and much stronger interaction strength, in support of the successful synthesis of highly stable curcumin-coated Gd nanoparticles as reported recently. It can be attributed to significant charge transfer from the Gd cluster to curcumin together with a relatively strong hybridization of the Gd df-orbitals with curcumin p-orbitals. These results suggest that Gd nanoparticles can effectively be used as delivery carriers for curcumin at the cellular level for therapy and medical imaging applications.

  2. Theoretical studies of the electronic structure of small metal clusters

    NASA Technical Reports Server (NTRS)

    Jordan, K. D.

    1982-01-01

    Theoretical studies of the electronic structure of metal clusters, in particular clusters of Group IIA and IIB atoms were conducted. Early in the project it became clear that electron correlation involving d orbitals plays a more important role in the binding of these clusters than had been previously anticipated. This necessitated that computer codes for calculating two electron integrals and for constructing the resulting CI Hamiltonions be replaced with newer, more efficient procedures. Program modification, interfacing and testing were performed. Results of both plans are reported.

  3. Reactivity of small transition-metal clusters with CO

    NASA Astrophysics Data System (ADS)

    Andersson, Mats T.; Gronbeck, H.; Holmgren, L.; Rosen, Arne

    1995-09-01

    The size-dependent reactivity of several transition-metal clusters: Con, Nbn, Rhn, and Wn with CO has been investigated in a cluster beam experiment. The reactions occur at single-collision-like conditions and the results are evaluated in terms of the reaction probability (S) in a collision. For all the four metals, clusters with more than 10 - 15 atoms show a high reaction probability, S >= 0.4, rather independent of size. For smaller Nbn and Wn, the reaction probability is lower, and for Nbn, large variations in the CO reactivity are observed in the n equals 8 - 13 range with a distinct minimum at Nb10. Using an LCAO approach within the local spin density approximation (LSDA) the adsorption of molecular CO on Nbn has also been investigated theoretically. The geometries of the bare clusters were optimized and two different sites for CO were investigated. The discussion is based on a detailed analysis of Nb4. The calculations show that compact structures with high coordination numbers are the most stable ones for the bare Nb clusters and hollow sites, also maximizing the coordination, are preferred for CO adsorption. The calculations indicate that a high CO-Nbn bond strength is obtained for clusters with a high density of states close to the Fermi level and for which the HOMO level has a symmetry that allows for an efficient back-donation of electrons to the 2(pi) *-orbital of CO. A particularly low chemisorption energy was calculated for the Nb10 cluster.

  4. Method of physical vapor deposition of metal oxides on semiconductors

    DOEpatents

    Norton, David P.

    2001-01-01

    A process for growing a metal oxide thin film upon a semiconductor surface with a physical vapor deposition technique in a high-vacuum environment and a structure formed with the process involves the steps of heating the semiconductor surface and introducing hydrogen gas into the high-vacuum environment to develop conditions at the semiconductor surface which are favorable for growing the desired metal oxide upon the semiconductor surface yet is unfavorable for the formation of any native oxides upon the semiconductor. More specifically, the temperature of the semiconductor surface and the ratio of hydrogen partial pressure to water pressure within the vacuum environment are high enough to render the formation of native oxides on the semiconductor surface thermodynamically unstable yet are not so high that the formation of the desired metal oxide on the semiconductor surface is thermodynamically unstable. Having established these conditions, constituent atoms of the metal oxide to be deposited upon the semiconductor surface are directed toward the surface of the semiconductor by a physical vapor deposition technique so that the atoms come to rest upon the semiconductor surface as a thin film of metal oxide with no native oxide at the semiconductor surface/thin film interface. An example of a structure formed by this method includes an epitaxial thin film of (001)-oriented CeO.sub.2 overlying a substrate of (001) Ge.

  5. Depositing nanometer-sized particles of metals onto carbon allotropes

    NASA Technical Reports Server (NTRS)

    Watson, Kent A. (Inventor); Fallbach, Michael J. (Inventor); Ghose, Sayata (Inventor); Smith, Joseph G. (Inventor); Delozier, Donavon M. (Inventor); Connell, John W. (Inventor)

    2010-01-01

    A process for depositing nanometer-sized metal particles onto a substrate in the absence of aqueous solvents, organic solvents, and reducing agents, and without any required pre-treatment of the substrate, includes preparing an admixture of a metal compound and a substrate by dry mixing a chosen amount of the metal compound with a chosen amount of the substrate; and supplying energy to the admixture in an amount sufficient to deposit zero valance metal particles onto the substrate. This process gives rise to a number of deposited metallic particle sizes which may be controlled. The compositions prepared by this process are used to produce polymer composites by combining them with readily available commodity and engineering plastics. The polymer composites are used as coatings, or they are used to fabricate articles, such as free-standing films, fibers, fabrics, foams, molded and laminated articles, tubes, adhesives, and fiber reinforced articles. These articles are well-suited for many applications requiring thermal conductivity, electrical conductivity, antibacterial activity, catalytic activity, and combinations thereof.

  6. Supersonic Bare Metal Cluster Beams. Technical Progress Report, March 16, 1984 - April 1, 1985

    DOE R&D Accomplishments Database

    Smalley, R. E.

    1985-01-01

    There have been four major areas of concentration for the study of bare metal cluster beams: neutral cluster, chemical reactivity, cold cluster ion source development (both positive and negative), bare cluster ion ICR (ion cyclotron resonance) development, and photofragmentation studies of bare metal cluster ions.

  7. From atoms to layers: in situ gold cluster growth kinetics during sputter deposition.

    PubMed

    Schwartzkopf, Matthias; Buffet, Adeline; Körstgens, Volker; Metwalli, Ezzeldin; Schlage, Kai; Benecke, Gunthard; Perlich, Jan; Rawolle, Monika; Rothkirch, André; Heidmann, Berit; Herzog, Gerd; Müller-Buschbaum, Peter; Röhlsberger, Ralf; Gehrke, Rainer; Stribeck, Norbert; Roth, Stephan V

    2013-06-07

    The adjustment of size-dependent catalytic, electrical and optical properties of gold cluster assemblies is a very significant issue in modern applied nanotechnology. We present a real-time investigation of the growth kinetics of gold nanostructures from small nuclei to a complete gold layer during magnetron sputter deposition with high time resolution by means of in situ microbeam grazing incidence small-angle X-ray scattering (μGISAXS). We specify the four-stage growth including their thresholds with sub-monolayer resolution and identify phase transitions monitored in Yoneda intensity as a material-specific characteristic. An innovative and flexible geometrical model enables the extraction of morphological real space parameters, such as cluster size and shape, correlation distance, layer porosity and surface coverage, directly from reciprocal space scattering data. This approach enables a large variety of future investigations of the influence of different process parameters on the thin metal film morphology. Furthermore, our study allows for deducing the wetting behavior of gold cluster films on solid substrates and provides a better understanding of the growth kinetics in general, which is essential for optimization of manufacturing parameters, saving energy and resources.

  8. Variable Stars In the Unusual, Metal-Rich Globular Cluster

    NASA Technical Reports Server (NTRS)

    Pritzl, Barton J.; Smith, Horace A.; Catelan, Marcio; Sweigart, Allen V.; Oegerle, William R. (Technical Monitor)

    2002-01-01

    We have undertaken a search for variable stars in the metal-rich globular cluster NGC 6388 using time-series BV photometry. Twenty-eight new variables were found in this survey, increasing the total number of variables found near NGC 6388 to approx. 57. A significant number of the variables are RR Lyrae (approx. 14), most of which are probable cluster members. The periods of the fundamental mode RR Lyrae are shown to be unusually long compared to metal-rich field stars. The existence of these long period RRab stars suggests that the horizontal branch of NGC 6388 is unusually bright. This implies that the metallicity-luminosity relationship for RR Lyrae stars is not universal if the RR Lyrae in NGC 6388 are indeed metal-rich. We consider the alternative possibility that the stars in NGC 6388 may span a range in [Fe/H]. Four candidate Population II Cepheids were also found. If they are members of the cluster, NGC 6388 would be the most metal-rich globular cluster to contain Population II Cepheids. The mean V magnitude of the RR Lyrae is found to be 16.85 +/- 0.05 resulting in a distance of 9.0 to 10.3 kpc, for a range of assumed values of (M(sub V)) for RR Lyrae. We determine the reddening of the cluster to be E(B - V) = 0.40 +/- 0.03 mag, with differential reddening across the face of the cluster. We discuss the difficulty in determining the Oosterhoff classification of NGC 6388 and NGC 6441 due to the unusual nature of their RR Lyrae, and address evolutionary constraints on a recent suggestion that they are of Oosterhoff type II.

  9. Developing gradient metal alloys through radial deposition additive manufacturing.

    PubMed

    Hofmann, Douglas C; Roberts, Scott; Otis, Richard; Kolodziejska, Joanna; Dillon, R Peter; Suh, Jong-ook; Shapiro, Andrew A; Liu, Zi-Kui; Borgonia, John-Paul

    2014-06-19

    Interest in additive manufacturing (AM) has dramatically expanded in the last several years, owing to the paradigm shift that the process provides over conventional manufacturing. Although the vast majority of recent work in AM has focused on three-dimensional printing in polymers, AM techniques for fabricating metal alloys have been available for more than a decade. Here, laser deposition (LD) is used to fabricate multifunctional metal alloys that have a strategically graded composition to alter their mechanical and physical properties. Using the technique in combination with rotational deposition enables fabrication of compositional gradients radially from the center of a sample. A roadmap for developing gradient alloys is presented that uses multi-component phase diagrams as maps for composition selection so as to avoid unwanted phases. Practical applications for the new technology are demonstrated in low-coefficient of thermal expansion radially graded metal inserts for carbon-fiber spacecraft panels.

  10. Biomonitoring of metal deposition in northern Spain by moss analysis.

    PubMed

    Fernández, J A; Ederra, A; Núñez, E; Martínez-Abaigar, J; Infante, M; Heras, P; Elías, M J; Mazimpaka, V; Carballeira, A

    2002-12-02

    The results of the first survey carried out in northern Spain to determine atmospheric deposition of metals by analysis of terrestrial mosses, are described. Samples of different mosses, mainly Hypnum cupressiforme and Scleropodium purum, were collected from 134 sampling sites, between 1995 and 1996. Levels of Al, As, Cr, Cu, Fe, Hg, Ni, Pb and Zn, were determined by flame atomic absorption or atomic fluorescence spectrophotometry. Regression analysis was used to compare the capacity of the selected moss species to accumulate the elements, and intercalibration of accumulation in these species was carried out where necessary. Distribution maps were prepared to allow the zones most affected by metal deposition to be identified and to relate this to known sources of contamination: electricity power stations and other industries (e.g. Hg and Ni), edaphic contamination (e.g. Al and Cr) and road traffic (Pb). Background levels of metals in each species were also determined for the study area.

  11. Developing Gradient Metal Alloys through Radial Deposition Additive Manufacturing

    PubMed Central

    Hofmann, Douglas C.; Roberts, Scott; Otis, Richard; Kolodziejska, Joanna; Dillon, R. Peter; Suh, Jong-ook; Shapiro, Andrew A.; Liu, Zi-Kui; Borgonia, John-Paul

    2014-01-01

    Interest in additive manufacturing (AM) has dramatically expanded in the last several years, owing to the paradigm shift that the process provides over conventional manufacturing. Although the vast majority of recent work in AM has focused on three-dimensional printing in polymers, AM techniques for fabricating metal alloys have been available for more than a decade. Here, laser deposition (LD) is used to fabricate multifunctional metal alloys that have a strategically graded composition to alter their mechanical and physical properties. Using the technique in combination with rotational deposition enables fabrication of compositional gradients radially from the center of a sample. A roadmap for developing gradient alloys is presented that uses multi-component phase diagrams as maps for composition selection so as to avoid unwanted phases. Practical applications for the new technology are demonstrated in low-coefficient of thermal expansion radially graded metal inserts for carbon-fiber spacecraft panels. PMID:24942329

  12. Litigated Metal Clusters - Structures, Energy and Reactivity

    DTIC Science & Technology

    2016-04-01

    Self Assembly: Novel Ion Mobility Methods Show the Essential Role of Water Do, T. D.; Bowers, M. T. Anal . Chem. 2015, 87, 4243–4252. 3. A New...Buffer Gas Bleiholder, C.; Johnson, N. R.; Contreras, S.; Wyttenbach, T.; Bowers, M. T. Anal . Chem. 2015, 87, 7196–7203. 5. Amino Acid Metaclusters...Bowers, M. T. Anal . Chem. 2016, 88, 868–876. Changes in research objectives (if any): The research objectives were changed from investigation of metal

  13. Hitomi observations of the Perseus Cluster / Constant metallicity in the outskirts of galaxy clusters

    NASA Astrophysics Data System (ADS)

    Werner, Norbert; Simionescu, Aurora; Urban, Ondrej; Allen, Steven

    2016-07-01

    X-ray observations with the Suzaku satellite reveal a remarkably homogeneous distribution of iron out to the virial radii of nearby galaxy clusters. Observations of the Virgo Cluster, that also allow us to measure the abundances of Si, S, and Mg out to the outskirts, show that the chemical composition of the intra-cluster medium is constant on large scales. These observations require that most of the metal enrichment and mixing of the intergalactic medium occurred before clusters formed, probably more than ten billion years ago, during the period of maximal star formation and black hole activity. We estimate the ratio between the number of SN Ia and the total number of supernovae enriching the intergalactic medium to be between 15-20%, generally consistent with the metal abundance patterns in our own Galaxy.

  14. Metallicity in the Galactic Center: The Arches Cluster

    NASA Astrophysics Data System (ADS)

    Najarro, Francisco; Figer, Donald F.; Hillier, D. John; Kudritzki, Rolf P.

    2004-04-01

    We present a quantitative spectral analysis of five very massive stars in the Arches cluster, located near the Galactic center, to determine stellar parameters, stellar wind properties, and, most importantly, metallicity content. The analysis uses a new technique, presented here for the first time, and uses line-blanketed non-LTE wind/atmosphere models fitted to high-resolution near-infrared spectra of late-type nitrogen-rich Wolf-Rayet stars and OfI+ stars in the cluster. It relies on the fact that massive stars reach a maximum nitrogen abundance that is related to initial metallicity when they are in the WNL phase. We determine the present-day nitrogen abundance of the WNL stars in the Arches cluster to be 1.6% (mass fraction) and constrain the stellar metallicity in the cluster to be solar. This result is invariant to assumptions about the mass-luminosity relationship, the mass-loss rates, and rotation speeds. In addition, from this analysis, we find the age of the Arches cluster to be 2-2.5 Myr, assuming coeval formation.

  15. Adsorption of heavy metals by road deposited solids.

    PubMed

    Gunawardana, Chandima; Goonetilleke, Ashantha; Egodawatta, Prasanna

    2013-01-01

    The research study discussed in the paper investigated the adsorption/desorption behaviour of heavy metals commonly deposited on urban road surfaces, namely, Zn, Cu, Cr and Pb, for different particle size ranges of solids. The study outcomes, based on field studies and batch experiments, confirmed that road deposited solids particles contain a significantly high amount of vacant charge sites with the potential to adsorb additional heavy metals. Kinetic studies and adsorption experiments indicated that Cr is the most preferred metal element to associate with solids due to the relatively high electronegativity and high charge density of trivalent cation (Cr(3+)). However, the relatively low availability of Cr in the urban road environment could influence this behaviour. Comparing total adsorbed metals present in solids particles, it was found that Zn has the highest capacity for adsorption to solids. Desorption experiments confirmed that a low concentration of Cu, Cr and Pb in solids was present in water-soluble and exchangeable form, whilst a significant fraction of adsorbed Zn has a high likelihood of being released back into solution. Among heavy metals, Zn is considered to be the most commonly available metal among road surface pollutants.

  16. Clustered field evaporation of metallic glasses in atom probe tomography.

    PubMed

    Zemp, J; Gerstl, S S A; Löffler, J F; Schönfeld, B

    2016-03-01

    Field evaporation of metallic glasses is a stochastic process combined with spatially and temporally correlated events, which are referred to as clustered evaporation (CE). This phenomenon is investigated by studying the distance between consecutive detector hits. CE is found to be a strongly localized phenomenon (up to 3nm in range) which also depends on the type of evaporating ions. While a similar effect in crystals is attributed to the evaporation of crystalline layers, CE of metallic glasses presumably has a different - as yet unknown - physical origin. The present work provides new perspectives on quantification methods for atom probe tomography of metallic glasses.

  17. Hydride encapsulation by molecular alkali-metal clusters.

    PubMed

    Haywood, Joanna; Wheatley, Andrew E H

    2008-07-14

    The sequential treatment of group 12 and 13 Lewis acids with alkali-metal organometallics is well established to yield so-called ''ate' complexes, whereby the Lewis-acid metal undergoes nucleophilic attack to give an anion, at least one group 1 metal acting to counter this charge. However, an alternative, less well recognised, reaction pathway involves the Lewis acid abstracting hydride from the organolithium reagent via a beta-elimination mechanism. It has recently been shown that in the presence of N,N'-bidentate ligands this chemistry can be harnessed to yield a new type of molecular main-group metal cluster in which the abstracted LiH is effectively trapped, with the hydride ion occupying an interstitial site in the cluster core. Discussion focuses on the development of this field, detailing advances in our understanding of the roles of Lewis acid, organolithium, and amine substrates in the syntheses of these compounds. Structure-types are discussed, as are efforts to manipulate cluster geometry and composition as well as hydride-coordination. Embryonic mechanistic studies are reported, as well as attempts to generate hydride-encapsulation clusters under catalytic control.

  18. Flexible macrocycles as versatile supports for catalytically active metal clusters

    DOE PAGES

    Ryan, Jason D.; Gagnon, Kevin J.; Teat, Simon J.; ...

    2016-02-12

    Here we present three structurally diverse clusters stabilised by the same macrocyclic polyphenol; t-butylcalix[8]arene. This work demonstrates the range of conformations the flexible ligand is capable of adopting, highlighting its versatility in metal coordination. In addition, a Ti complex displays activity for the ring-opening polymerisation of lactide

  19. Flexible macrocycles as versatile supports for catalytically active metal clusters

    SciTech Connect

    Ryan, Jason D.; Gagnon, Kevin J.; Teat, Simon J.; McIntosh, Ruaraidh D.

    2016-02-12

    Here we present three structurally diverse clusters stabilised by the same macrocyclic polyphenol; t-butylcalix[8]arene. This work demonstrates the range of conformations the flexible ligand is capable of adopting, highlighting its versatility in metal coordination. In addition, a Ti complex displays activity for the ring-opening polymerisation of lactide

  20. Structure of fluorescent metal clusters on a DNA template.

    NASA Astrophysics Data System (ADS)

    Vdovichev, A. A.; Sych, T. S.; Reveguk, Z. V.; Smirnova, A. A.; Maksimov, D. A.; Ramazanov, R. R.; Kononov, A. I.

    2016-08-01

    Luminescent metal clusters are a subject of growing interest in recent years due to their bright emission from visible to near infrared range. Detailed structure of the fluorescent complexes of Ag and other metal clusters with ligands still remains a challenging task. In this joint experimental and theoretical study we synthesized Ag-DNA complexes on a DNA oligonucleotide emitting in violet- green spectral range. The structure of DNA template was determined by means of various spectral measurements (CD, MS, XPS). Comparison of the experimental fluorescent excitation spectra and calculated absorption spectra for different QM/MM optimized structures allowed us to determine the detailed structure of the green cluster containing three silver atoms in the stem of the DNA hairpin structure stabilized by cytosine-Ag+-cytosine bonds.

  1. Nanoscale electrodeposition of low-dimensional metal phases and clusters.

    PubMed

    Staikov, Georgi

    2016-08-07

    The present status of the problem of electrochemical formation of low-dimensional metal phases is reviewed. The progress in this field achieved in the last two decades is discussed on the basis of experimental results obtained in selected electrochemical systems with well defined single crystal substrates. The influence of crystallographic orientation and surface inhomogeneities of foreign substrates on the mechanism of formation and the atomic structure of two-dimensional (2D) metal phases in the underpotential deposition range is considered. The localized electrodeposition of metal nanoclusters on solid state surfaces applying the STM-tip as a nanoelectrode is demonstrated.

  2. Nanoscale electrodeposition of low-dimensional metal phases and clusters

    NASA Astrophysics Data System (ADS)

    Staikov, Georgi

    2016-07-01

    The present status of the problem of electrochemical formation of low-dimensional metal phases is reviewed. The progress in this field achieved in the last two decades is discussed on the basis of experimental results obtained in selected electrochemical systems with well defined single crystal substrates. The influence of crystallographic orientation and surface inhomogeneities of foreign substrates on the mechanism of formation and the atomic structure of two-dimensional (2D) metal phases in the underpotential deposition range is considered. The localized electrodeposition of metal nanoclusters on solid state surfaces applying the STM-tip as a nanoelectrode is demonstrated.

  3. Numerical Simulations of Particle Deposition in Metal Foam Heat Exchangers

    NASA Astrophysics Data System (ADS)

    Sauret, Emilie; Saha, Suvash C.; Gu, Yuantong

    2013-01-01

    Australia is a high-potential country for geothermal power with reserves currently estimated in the tens of millions of petajoules, enough to power the nation for at least 1000 years at current usage. However, these resources are mainly located in isolated arid regions where water is scarce. Therefore, wet cooling systems for geothermal plants in Australia are the least attractive solution and thus air-cooled heat exchangers are preferred. In order to increase the efficiency of such heat exchangers, metal foams have been used. One issue raised by this solution is the fouling caused by dust deposition. In this case, the heat transfer characteristics of the metal foam heat exchanger can dramatically deteriorate. Exploring the particle deposition property in the metal foam exchanger becomes crucial. This paper is a numerical investigation aimed to address this issue. Two-dimensional (2D) numerical simulations of a standard one-row tube bundle wrapped with metal foam in cross-flow are performed and highlight preferential particle deposition areas.

  4. Atomic resolution electron microscopy of small metal clusters

    NASA Astrophysics Data System (ADS)

    Bovin, J.-O.; Malm, J.-O.

    1991-03-01

    Atomic resolution imaging of cluster structures has been performed with high resolution transmission electron microscopy (HRTEM). Metal particles of the sizes 1 nanometer to tens of nanometers have been surface profile imaged on different supports; like zeolites, cordierite and amorphous carbon. It is shown that organic ligands in Schmid-clusters coordinated to the metal surface are desorbed or destroyed by the electron beam. Dynamic events on the surfaces and in the bulk of small metal particles have been recorded for small crystals of Au, Pt, Rh and Pb and can be classified under three headings; The smaller the crystals are the faster rearrangements of the crystal structure; “clouds” of atoms existing outside some surfaces are involved in extensive structural rearrangements of the surface or crystal surface growth; localized atom hopping on surfaces during crystal growth and desorption also occurs.

  5. Excited state reactions of metals in clusters: pluridimensional harpoon and solvation effects.

    PubMed

    Briant, M; Gaveau, M A; Fournier, P R; Mestdagh, J M; Visticot, J P; Soep, B

    2001-01-01

    Excited state reactions of metals produce electronically excited products efficiently, as revealed by studies performed both in the gas phase and in free Van der Waals complexes. The reaction mechanism is assigned to an excited state charge transfer from the metal to the molecular reactant (i.e. a harpoon mechanism). The present work uses the well established cluster isolated chemical reaction (CICR) technique and addresses these processes when the metal ... molecule Van der Waals pair is deposited at the surface of a large argon cluster. Such work is aimed at investigating the effect of the cluster substrate on the preparation and dynamics of the reaction. We have revisited the pluridimensional character of the harpoon reaction in these systems. More specifically, we studied the reaction of excited calcium with HBr near the calcium resonance line at 422.7 nm, forming CaBr in the A and B states. As in previous Van der Waals experiments, we could explore the dynamics of the reaction by recording action spectra. These spectra exhibit noticeable differences from those observed for unsupported Ca...HBr complexes. In particular the bending movement of the Ca...HBr complex which gives access to the transition state of the reaction is partly hindered by the presence of the argon cluster.

  6. Innovations in laser cladding and direct metal deposition

    NASA Astrophysics Data System (ADS)

    Brückner, Frank; Nowotny, Steffen; Leyens, Christoph

    2012-03-01

    The present paper reviews recent progress in productivity, precision and quality of laser-based cladding and additive layer manufacturing. Recently, we have demonstrated the great benefits obtained from induction assisted laser cladding. This novel hybrid technology combines high deposition rates with excellent cladding properties. Laser-based direct metal deposition is a novel concept for the fabrication of components and repair as well as geometrical surface modifications. Newly developed nozzle design allows focused powder spots to generate wall thicknesses of about 30 μm. An in-depth understanding of the processes and the resulting materials properties is key for the development of technically viable and economically reasonable customized solutions.

  7. The Dielectric Breakdown Model applied to explain various morphologies of deposited metallic structures in thin gap metal electro-deposition

    NASA Astrophysics Data System (ADS)

    Chowdhury, Aditya; Dutta, Dibakar

    2015-06-01

    The phenomenon of metal electro-deposition in thin-gap geometry leads to very interesting and diverse two dimensional morphologies. This varies from dense ramified growth to thin dendritic projections. In this paper, we have proposed a stochastic model that incorporates such diversity. We carried out thin-gap electro-deposition of Copper and Zinc with varying electrolytic concentrations. A well known model, that until this work was used to explain dielectric breakdown patterns, was employed to explain the variation in deposition morphology with concentration. The sole parameter in the model was varied and the numerically obtained patterns was seen to correlate well with those obtained from electro-deposition. A linear relationship between the parameter and molar concentration was established. The established relationship was then analysed and interpreted.

  8. Characterization of oxide supported metal carbonyl clusters

    NASA Astrophysics Data System (ADS)

    Evans, John

    The chemisorption of [Ma 3(CO) 1 2] on silica (M = Ru and Os) and alumina (M = Os) has been studied by vibrational and X-ray absorption spectroscopies making close comparisons with model compounds. The results indicate that the first chemisorption species observed has the form [M 3H(CO) 10(O---O)]; the bridging hydride was observed directly for the silica systems as evidenced by the M-H-M bending vibration in the i.r. Also consistent with this structure are the EXAFS analysis of the Ru/SiOz material. This indicated an essentially equilateral ruthenium triangle and coordination to oxygen. The published low frequency Raman data on the Os/Al2Oa product was shown to match most closely with that of model compounds with a bidentate oxygen donor ligand (acac or O2CR). The tethered cluster [O s3H 2(CO) 9(PPh 2C 2H 4SIL)] was found to be a relatively short lived species on a silica surface. Under ambient conditions it reacts further and the i.r., EXAFS and 31P NMR data of this species suggest that the two osmium atoms not coordinated to the tethering phosphine become involved with a bidentate site from the surface.

  9. Cooperative Cluster Metalation and Ligand Migration in Zirconium Metal-Organic Frameworks.

    PubMed

    Yuan, Shuai; Chen, Ying-Pin; Qin, Junsheng; Lu, Weigang; Wang, Xuan; Zhang, Qiang; Bosch, Mathieu; Liu, Tian-Fu; Lian, Xizhen; Zhou, Hong-Cai

    2015-12-01

    Cooperative cluster metalation and ligand migration were performed on a Zr-MOF, leading to the isolation of unique bimetallic MOFs based on decanuclear Zr6M4 (M = Ni, Co) clusters. The M(2+) reacts with the μ3-OH and terminal H2O ligands on an 8-connected [Zr6O4(OH)8(H2O)4] cluster to form a bimetallic [Zr6M4O8(OH)8(H2O)8] cluster. Along with the metalation of Zr6 cluster, ligand migration is observed in which a Zr-carboxylate bond dissociates to form a M-carboxylate bond. Single-crystal to single-crystal transformation is realized so that snapshots for cooperative cluster metalation and ligand migration processes are captured by successive single-crystal X-ray structures. In(3+) was metalated into the same Zr-MOF which showed excellent catalytic activity in the acetaldehyde cyclotrimerization reaction. This work not only provides a powerful tool to functionalize Zr-MOFs with other metals, but also structurally elucidates the formation mechanism of the resulting heterometallic MOFs. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. The Corrosion Protection of Metals by Ion Vapor Deposited Aluminum

    NASA Technical Reports Server (NTRS)

    Danford, M. D.

    1993-01-01

    A study of the corrosion protection of substrate metals by ion vapor deposited aluminum (IVD Al) coats has been carried out. Corrosion protection by both anodized and unanodized IVD Al coats has been investigated. Base metals included in the study were 2219-T87 Al, 7075-T6 Al, Titanium-6 Al-4 Vanadium (Ti-6Al-4V), 4130 steel, D6AC steel, and 4340 steel. Results reveal that the anodized IVD Al coats provide excellent corrosion protection, but good protection is also achieved by IVD Al coats that have not been anodized.

  11. The corrosion protection of metals by ion vapor deposited aluminum

    SciTech Connect

    Danford, M.D.

    1993-10-01

    A study of the corrosion protection of substrate metals by ion vapor deposited aluminum (IVD Al) coats has been carried out. Corrosion protection by both anodized and unanodized IVD Al coats has been investigated. Base metals included in the study were 2219-T87 Al, 7075-T6 Al, Titanium-6 Al-4 Vanadium (Ti-6Al-4V), 4130 steel, D6AC steel, and 4340 steel. Results reveal that the anodized IVD Al coats provide excellent corrosion protection, but good protection is also achieved by IVD Al coats that have not been anodized.

  12. Long-lived excited states in metal clusters.

    PubMed

    Koop, Alexander; Gantefoer, Gerd; Kim, Young Dok

    2017-08-16

    Bare metal clusters have properties that make them interesting for applications in photochemistry and photovoltaics. Long-lived excited states are a prerequisite for such applications, because in them the energy of the photon can be stored. Clusters have a low density of states and long-lived excited states should therefore occur frequently. However, in fact, such states are a rarity, as indicated by time-resolved photoelectron data of mass-selected cluster anions. And there is another puzzling observation: only clusters with narrow peaks in their photoelectron spectra exhibit long-lived excited states. Both findings can be explained if internal conversion, i.e. the conversion of electronic excitation energy into vibrational excitations, is the major relaxation mechanism in clusters. It becomes more likely, if a change of the electronic configuration results in a large geometry change, which is probably the case for most clusters. Only clusters with a weak coupling between geometric and electronic structure may have long-lived excited states and narrow peaks.

  13. Evolution of metallic screening in small metal clusters probed by PCI-Auger spectroscopy.

    PubMed

    Peters, Sven; Peredkov, Sergey; Balkaya, Baris; Ferretti, Nicoletta; Neeb, Matthias; Eberhardt, Wolfgang

    2010-09-07

    Excitation-energy dependent Auger spectra of small copper clusters supported by a thin silica layer have been measured as function of cluster size. The Auger kinetic energy of the clusters clearly changes with the excess energy of the emitted photoelectron while not for the bulk. The kinetic energy shift is attributed to post-collision interaction (PCI) and exhibits a reduced metallic screening ability of small Cu-clusters. The spectroscopic data reveal an evolution from a long-range Coulomb-like interaction to a short-range "screened" electrostatic interaction within the sub-nm range. The data show that core electron spectroscopy such as PCI-Auger measurements can be used as a general tool to follow the metallic character of supported clusters.

  14. Spectroscopy at metal cluster surfaces. Final report, September 15, 1993--September 14, 1996

    SciTech Connect

    Duncan, M.A.

    1998-06-01

    The focus of this research program is the study of gas phase metal clusters to evaluate their potential as models for the fundamental interactions present in catalysis. To do this, the authors characterize the chemical bonding present between the component atoms in metal clusters as well as the bonding exhibited by {open_quotes}physisorption{close_quotes} on metal atom or metal cluster surfaces. Electronic spectra, vibrational frequencies and bond dissociation energies are measured for both neutral and ionized clusters with a variety of laser/mass spectrometry techniques. The authors are particularly interested in bimetallic cluster systems, and how their properties compare to those of corresponding pure metal clusters.

  15. Process for electrolytic deposition of metals on zirconium materials

    DOEpatents

    Donaghy, Robert E.

    1979-01-30

    A process for the electrolytic deposition of a metal layer on an article comprised of zirconium or a zirconium alloy is disclosed. The article is activated in an aged aqueous solution comprising from about 10 to about 20 grams per liter ammonium bifluoride and from about 0.75 to about 2 grams per liter of sulfuric acid. The solution is aged by immersion of pickled zirconium in the solution for at least about 10 minutes. The loosely adhering film formed on the article in the activating step is removed and the article is contacted with an electrolytic plating solution containing the metal to be deposited on the article in the presence of an electrode receiving current.

  16. Process for electroless deposition of metals on zirconium materials

    DOEpatents

    Donaghy, Robert E.

    1978-01-01

    A process for the electroless deposition of a metal layer on an article comprised of zirconium or a zirconium alloy is disclosed. The article is activated in an aged aqueous solution comprising from about 10 to about 20 grams per liter ammonium bifluoride and from about 0.75 to about 2 grams per liter of sulfuric acid. The solution is aged by immersion of pickled zirconium in the solution for at least about 10 minutes. The loosely adhering film formed on the article in the activating step is removed and the article is contacted with an electroless plating solution containing the metal to be deposited on the article upon sufficient contact with the article.

  17. Selective metal deposition at graphene line defects by atomic layer deposition

    NASA Astrophysics Data System (ADS)

    Kim, Kwanpyo; Lee, Han-Bo-Ram; Johnson, Richard W.; Tanskanen, Jukka T.; Liu, Nan; Kim, Myung-Gil; Pang, Changhyun; Ahn, Chiyui; Bent, Stacey F.; Bao, Zhenan

    2014-09-01

    One-dimensional defects in graphene have a strong influence on its physical properties, such as electrical charge transport and mechanical strength. With enhanced chemical reactivity, such defects may also allow us to selectively functionalize the material and systematically tune the properties of graphene. Here we demonstrate the selective deposition of metal at chemical vapour deposited graphene’s line defects, notably grain boundaries, by atomic layer deposition. Atomic layer deposition allows us to deposit Pt predominantly on graphene’s grain boundaries, folds and cracks due to the enhanced chemical reactivity of these line defects, which is directly confirmed by transmission electron microscopy imaging. The selective functionalization of graphene defect sites, together with the nanowire morphology of deposited Pt, yields a superior platform for sensing applications. Using Pt-graphene hybrid structures, we demonstrate high-performance hydrogen gas sensors at room temperature and show its advantages over other evaporative Pt deposition methods, in which Pt decorates the graphene surface non-selectively.

  18. Method of preparing size-selected metal clusters

    DOEpatents

    Elam, Jeffrey W.; Pellin, Michael J.; Stair, Peter C.

    2010-05-11

    The invention provides a method for depositing catalytic clusters on a surface, the method comprising confining the surface to a controlled atmosphere; contacting the surface with catalyst containing vapor for a first period of time; removing the vapor from the controlled atmosphere; and contacting the surface with a reducing agent for a second period of time so as to produce catalyst-containing nucleation sites.

  19. Development of Metal Cluster-Based Energetic Materials

    NASA Astrophysics Data System (ADS)

    Lightstone, James; Hooper, Joseph; Stoltz, Chad; Wilson, Becca; Mayo, Dennis; Eichhorn, Bryan; Bowen, Kit

    2011-06-01

    The energy available from the combustion of Al is 2 to 3 times that of conventional high explosives and as a result is often loaded into explosive and propellant formulations in micron and nano-particle form. However, even at the nano-scale the release of energy is slowed by the reaction kinetics of particle oxidation. In order to realize faster reaction rates, on the order of current CHNO explosives, the size of the particles of interest need to be reduced significantly into the molecular size-range (10's of atoms). Current research efforts at NSWC-IHD are utilizing gas-phase molecular beam studies, theoretical calculations, and condensed-phase production methods to identify novel metal cluster systems in which passivated metal clusters make up the subunit of a molecular metal-based energetic material. To date, small amounts of a metal-based compound with a subunit containing four Al atoms and four Cp* ligands has been produced and is currently being characterized using DSC and TGA. Additional Al based systems passivated with a variety of organic ligands are being systematically examined. Analytical and theoretical results obtained for Al4Cp*4 and the additional cluster systems under investigation along with their potential energetic applications will be presented.

  20. Photochemical deposition of thin films from the metal hexacarbonyls

    SciTech Connect

    Singmaster K.A.; Houle, F.A.; Wilson, R.J. )

    1990-08-23

    Metal films grown by photolysis of Cr, Mo, and W hexacarbonyls are known to contain large amounts of carbon and oxygen, suggesting incomplete removal of CO from the precursor as well as possible reactions with other sources of carbon and oxygen. In order to identify microscopic processes responsible for film composition, a systematic study of thin films photochemically deposited by continuous, low-power 257-nm light from Cr, Mo, and W hexacarbonyls has been carried out. Since photodissociation of the precursor can occur on the surface as well as in the gas phase, experimental conditions have been chosen such that surface reaction kinetics are rate limiting. The experiments show that background gases during deposition and exposure of newly deposited films to air both result in significant oxidation of the films through their entire thickness, as determined by scanning Auger microscopy and sputter depth profiling. The results are discussed in terms of studies of photolysis of the metal hexacarbonyls and dissociative chemisorption of CO on clean crystalline metal surfaces.

  1. Electronic Structure and Properties of Metal Cluster Isomers

    NASA Astrophysics Data System (ADS)

    Jena, Puru

    1997-03-01

    One of the most interesting features of clusters is that they exhibit many isomeric forms. The geometries, binding energies, and electronic structure of isomers of alkali and transition metal clusters have been studied using first principles calculations based on molecular orbital theory. The existence of energetically degenerate isomers manifests in many novel features in photoelectron spectroscopy, reactivity, and magnetic properties. The theoretical results will be used not only to explain recent anomalous experimental data but also to predict phenomena that could be verified by future experiments.

  2. Inhibiting Metal Oxide Atomic Layer Deposition: Beyond Zinc Oxide.

    PubMed

    Sampson, Matthew D; Emery, Jonathan D; Pellin, Michael J; Martinson, Alex B F

    2017-04-05

    Atomic layer deposition (ALD) of several metal oxides is selectivity inhibited on alkanethiol self-assembled monolayers (SAMs) on Au, and the eventual nucleation mechanism is investigated. The inhibition ability of the SAM is significantly improved by the in situ H2-plasma pretreatment of the Au substrate prior to the gas-phase deposition of a long-chain alkanethiol, 1-dodecanethiol (DDT). This more rigorous surface preparation inhibits even aggressive oxide ALD precursors, including trimethylaluminum and water, for at least 20 cycles. We study the effect that the ALD precursor purge times, growth temperature, alkanethiol chain length, alkanethiol deposition time, and plasma treatment time have on Al2O3 ALD inhibition. This is the first example of Al2O3 ALD inhibition from a vapor-deposited SAM. The inhibitions of Al2O3, ZnO, and MnO ALD processes are compared, revealing the versatility of this selective surface treatment. Atomic force microscopy and grazing-incidence X-ray fluorescence further reveal insight into the mechanism by which the well-defined surface chemistry of ALD may eventually be circumvented to allow metal oxide nucleation and growth on SAM-modified surfaces.

  3. Direct observation of small cluster mobility and ripening. [during annealing of metal films on amorphous substrates

    NASA Technical Reports Server (NTRS)

    Heinemann, K.; Poppa, H.

    1975-01-01

    Direct evidence is reported for the simultaneous occurrence of Ostwald ripening and short-distance cluster mobility during annealing of discontinuous metal films on clean amorphous substrates. The annealing characteristics of very thin particulate deposits of silver on amorphized clean surfaces of single crystalline thin graphite substrates were studied by in-situ transmission electron microscopy (TEM) under controlled environmental conditions (residual gas pressure of 10 to the minus 9th power torr) in the temperature range from 25 to 450 C. Sputter cleaning of the substrate surface, metal deposition, and annealing were monitored by TEM observation. Pseudostereographic presentation of micrographs in different annealing stages, the observation of the annealing behavior at cast shadow edges, and measurements with an electronic image analyzing system were employed to aid the visual perception and the analysis of changes in deposit structure recorded during annealing. Slow Ostwald ripening was found to occur in the entire temperature range, but the overriding surface transport mechanism was short-distance cluster mobility.

  4. First-principles studies on graphene-supported transition metal clusters

    SciTech Connect

    Sahoo, Sanjubala Khanna, Shiv N.; Gruner, Markus E.; Entel, Peter

    2014-08-21

    Theoretical studies on the structure, stability, and magnetic properties of icosahedral TM{sub 13} (TM = Fe, Co, Ni) clusters, deposited on pristine (defect free) and defective graphene sheet as well as graphene flakes, have been carried out within a gradient corrected density functional framework. The defects considered in our study include a carbon vacancy for the graphene sheet and a five-membered and a seven-membered ring structures for graphene flakes (finite graphene chunks). It is observed that the presence of defect in the substrate has a profound influence on the electronic structure and magnetic properties of graphene-transition metal complexes, thereby increasing the binding strength of the TM cluster on to the graphene substrate. Among TM{sub 13} clusters, Co{sub 13} is absorbed relatively more strongly on pristine and defective graphene as compared to Fe{sub 13} and Ni{sub 13} clusters. The adsorbed clusters show reduced magnetic moment compared to the free clusters.

  5. Understanding and Practical Use of Ligand and Metal Exchange Reactions in Thiolate-Protected Metal Clusters to Synthesize Controlled Metal Clusters.

    PubMed

    Niihori, Yoshiki; Hossain, Sakiat; Sharma, Sachil; Kumar, Bharat; Kurashige, Wataru; Negishi, Yuichi

    2017-05-01

    It is now possible to accurately synthesize thiolate (SR)-protected gold clusters (Aun (SR)m ) with various chemical compositions with atomic precision. The geometric structure, electronic structure, physical properties, and functions of these clusters are well known. In contrast, the ligand or metal atom exchange reactions between these clusters and other substances have not been studied extensively until recently, even though these phenomena were observed during early studies. Understanding the mechanisms of these reactions could allow desired functional metal clusters to be produced via exchange reactions. Therefore, we have studied the exchange reactions between Aun (SR)m and analogous clusters and other substances for the past four years. The results have enabled us to gain deep understanding of ligand exchange with respect to preferential exchange sites, acceleration means, effect on electronic structure, and intercluster exchange. We have also synthesized several new metal clusters using ligand and metal exchange reactions. In this account, we summarize our research on ligand and metal exchange reactions. © 2017 The Chemical Society of Japan & Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Research on the processing experiments of laser metal deposition shaping

    NASA Astrophysics Data System (ADS)

    Zhang, Kai; Liu, Weijun; Shang, Xiaofeng

    2007-04-01

    Laser additive direct deposition of metals is a new rapid manufacturing technology, which combines with computer-aided design (CAD), laser cladding and rapid prototyping. The advanced technology can build fully dense metal components directly from CAD files with neither mould nor tool. Based on the theory of this technology, a promising rapid manufacturing system called "Laser Metal Deposition Shaping (LMDS)" has been constructed and developed successfully by Chinese Academy of Sciences, Shenyang Institute of Automation. Through the LMDS system, comprehensive experiments are carried out with nickel-based superalloy to systematically investigate the influences of the processing parameters on forming characteristics. By adjusting to the optimal processing parameters, fully dense and near-net-shaped metallic parts can be directly obtained through melting coaxially fed powder with a laser. Moreover, the microstructure and mechanical properties of as-formed samples are tested and analyzed synthetically. As a result, significant processing flexibility with the LMDS system over conventional processing capabilities is recognized, with potentially lower production cost, higher quality components, and shorter lead-time.

  7. Globular Cluster Systems in Brightest Cluster Galaxies: Bimodal Metallicity Distributions and the Nature of the High-Luminosity Clusters

    NASA Astrophysics Data System (ADS)

    Harris, William E.; Whitmore, Bradley C.; Karakla, Diane; Okoń, Waldemar; Baum, William A.; Hanes, David A.; Kavelaars, J. J.

    2006-01-01

    We present new (B, I) photometry for the globular cluster systems in eight brightest cluster galaxies (BCGs), obtained with the ACS/WFC camera on the Hubble Space Telescope. In the very rich cluster systems that reside within these giant galaxies, we find that all have strongly bimodal color distributions that are clearly resolved by the metallicity-sensitive (B-I) index. Furthermore, the mean colors and internal color range of the blue subpopulation are remarkably similar from one galaxy to the next, to well within the +/-0.02-0.03 mag uncertainties in the foreground reddenings and photometric zero points. By contrast, the mean color and internal color range for the red subpopulation differ from one galaxy to the next by twice as much as the blue population. All the BCGs show population gradients, with much higher relative numbers of red clusters within 5 kpc of their centers, consistent with their having formed at later times than the blue, metal-poor population. A striking new feature of the color distributions emerging from our data is that for the brightest clusters (MI<-10.5) the color distribution becomes broad and less obviously bimodal. This effect was first noticed by Ostrov et al. and Dirsch et al. for the Fornax giant NGC 1399; our data suggest that it may be a characteristic of many BCGs and perhaps other large galaxies. Our data indicate that the blue (metal-poor) clusters brighter than MI~=-10 become progressively redder with increasing luminosity, following a mass/metallicity scaling relation Z~M0.55. A basically similar relation has been found for M87 by Strader et al. (2005). We argue that these GCS characteristics are consistent with a hierarchical-merging galaxy formation picture in which the metal-poor clusters formed in protogalactic clouds or dense starburst complexes with gas masses in the range 107-1010 Msolar, but where the more massive clusters on average formed in bigger clouds with deeper potential wells where more preenrichment could

  8. Si clusters are more metallic than bulk Si

    NASA Astrophysics Data System (ADS)

    Jackson, Koblar; Jellinek, Julius

    2016-12-01

    Dipole polarizabilities were computed using density functional theory for silicon clusters over a broad range of sizes up to N = 147 atoms. The calculated total effective polarizabilities, which include contributions from permanent dipole moments of the clusters, are in very good agreement with recently measured values. We show that the permanent dipole contributions are most important for clusters in the intermediate size range and that the measured polarizabilities can be used to distinguish between energetically nearly degenerate cluster isomers at these sizes. We decompose the computed total polarizabilities α into the so-called dipole and charge transfer contributions, αp and αq, using a site-specific analysis. When the per-atom values of these quantities are plotted against N-1 /3, clear linear trends emerge that can be extrapolated to the large size limit (N-1 /3→0 ), resulting in a value for α/N of 30.5 bohrs3/atom that is significantly larger than the per-atom polarizability of semiconducting bulk Si, 25.04 bohrs3/atom. This indicates that Si clusters possess a higher degree of metallicity than bulk Si, a conclusion that is consistent with the strong electrostatic screening of the cluster interiors made evident by the analysis of the calculated atomic polarizabilities.

  9. The lifetime of electronic excitations in metal clusters

    NASA Astrophysics Data System (ADS)

    Quijada, M.; Díez Muiño, R.; Echenique, P. M.

    2005-05-01

    Density functional theory and the self-energy formalism are used to evaluate the lifetime of electronic excitations in metal clusters of nanometre size. The electronic structure of the cluster is obtained in the jellium model and spherical symmetry is assumed. Two effects that depend on the size of the clusters are discussed: the change in the number of final states to which the excitation can decay, and the modification in the screened interaction between electrons. For clusters with density parameter rs = 4 and diameter a few nanometres, a lifetime value of {\\approx }5 fs is reached for electronic excitations of {\\approx }1 eV. This value is of the same order of magnitude of that obtained in the bulk limit at the same level of approximation. For smaller clusters, a distinct non-monotonic behaviour of the lifetime as a function of the cluster size is found and the lifetime of excitations of {\\approx }1 eV can vary between 4 and 30 fs.

  10. Controlling the orientations of h-BN during growth on transition metals by chemical vapor deposition.

    PubMed

    Zhao, Ruiqi; Zhao, Xiaolei; Liu, Zhirong; Ding, Feng; Liu, Zhongfan

    2017-03-09

    Hexagonal boron nitride (h-BN) is crucial for many applications, and its synthesis over a large area with high quality is strongly desired. A promising approach to synthesize h-BN is chemical vapor deposition on transition metal catalysts, in which the alignments of BN clusters in the initial growth determine both the types and the amounts of defects in h-BN. In the search for a better catalyst, we systematically studied the interactions between h-BN clusters and various metal surfaces. Our results show that the clusters on nearly all catalyst surfaces, no matter whether the (111) facets of face-centered cubic (FCC) metals or the (0001) facets of hexagonal close packed (HCP) metals, have two local minima with opposite orientations. During the initial growth, h-BN clusters adopt the energy-favored sites, whose registry is well preserved upon further growth owing to the strong interaction between the edge atoms of h-BN and the underlying substrates. On FCC(111), the h-BN domains are always aligned in parallel orientations, while on HCP(0001) they are parallel on the same terrace and anti-parallel on neighboring terraces. Beyond this, on the (111) surfaces of Ir and Rh, the BhNt configuration is much more energy favorable than BfNt, where, the subscripts h, t, and f represent the adsorption sites, hcp, top and fcc, respectively. Thus, Ir(111) and Rh(111) might promote the growth of h-BN domains with the same alignments, which will greatly improve the quality of h-BN by reducing the possibility of formation of grain boundaries.

  11. Metallicity of Globular Cluster M13 from VI CCD Photometry

    NASA Astrophysics Data System (ADS)

    Shon, Young-Jong

    2000-12-01

    From the VI images of M13, obtained by using 2K CCD camera and the BOAO 1.8m telescope, we derive the (V-I)-V CMD of M13. From the shapes of red giant branch, the magnitude of horizontal branch, and the giant branch bump on the constructed CMD, we determined the metallicity of the globular cluster to be 1.74 ~<[Fe/H]~< -1.41. The good agreement between our determination of [Fe/H] and those determined by using other methods implies that the morphology of red giant and horizontal branches on (V-I)-V CMD's can be good indirect metallicity indicators of Galactic globular clusters.

  12. Chemical vapor deposition of metal diboride and metal oxide thin films from borohydride-bonded precursors

    NASA Astrophysics Data System (ADS)

    Yang, Yu

    Metal borohydrides denotes the type of metal complex in which the metals are connected to the surrounding ligands through boron-hydrogen bridge bonds. They are excellent CVD precursors owning to their outstanding volatility and high reactivity. Transition metal diboride and metal oxide thin films suitable for various technological applications are deposited from these novel precursors. In this dissertation, comprehensive investigations of thin film growth rate, composition, and properties as a function of precursor pressure and substrate temperature were carried out for the CVD of HfB2 and MgO. It is determined that their CVD growth kinetics can be well explained with a Langmuir surface reaction mechanism. A structure zone model is proposed to explain the microstructure-process relationship of the CVD thin films in general. In future generations of microelectronics fabrication, materials need to be deposited into recess features with smaller dimensions and higher aspect ratios. A new approach is developed to obtain super-conformal coating (bottom-up filling) of such high aspect ratio features. The super-conformal growth is demonstrated in the CVD of CrB2 and HfB2 films from the corresponding borohydride precursors with atomic and molecular growth suppressors. Computer simulation is employed to understand the mechanism of the super-conformal deposition. The high Tc superconductor MgB2 were deposited at low temperatures (T = 300°C--400°C) from a recently developed highly volatile borohydride-bonded Mg precursor, by means of catalyst-enhanced chemical vapor deposition. The films are stoichiometric and highly crystallized, however, the lattice constants shift away from the MgB2 structure to the diboride structure of the catalyst metal, suggesting that Mg is partially substituted by the corresponding metals.

  13. Scattering of ultrashort electromagnetic pulses on metal clusters

    SciTech Connect

    Astapenko, V. A. Sakhno, S. V.

    2016-12-15

    We have calculated and analyzed the probability of ultrashort electromagnetic pulse (USP) scattering on small metal clusters in the frequency range of plasmon resonances during the field action. The main attention is devoted to dependence of the probability of scattering on the pulse duration for various detunings of the USP carrier frequency from the plasmon resonance frequency. Peculiarities of the USP scattering from plasmon resonances with various figures of merit are revealed.

  14. NGC 1252: a high altitude, metal poor open cluster remnant

    NASA Astrophysics Data System (ADS)

    de la Fuente Marcos, R.; de la Fuente Marcos, C.; Moni Bidin, C.; Carraro, G.; Costa, E.

    2013-09-01

    If stars form in clusters but most stars belong to the field, understanding the details of the transition from the former to the latter is imperative to explain the observational properties of the field. Aging open clusters are one of the sources of field stars. The disruption rate of open clusters slows down with age but, as an object gets older, the distinction between the remaining cluster or open cluster remnant (OCR) and the surrounding field becomes less and less obvious. As a result, finding good OCR candidates or confirming the OCR nature of some of the best candidates still remain elusive. One of these objects is NGC 1252, a scattered group of about 20 stars in Horologium. Here we use new wide-field photometry in the UBVI passbands, proper motions from the Yale/San Juan SPM 4.0 catalogue and high-resolution spectroscopy concurrently with results from N-body simulations to decipher NGC 1252's enigmatic character. Spectroscopy shows that most of the brightest stars in the studied area are chemically, kinematically and spatially unrelated to each other. However, after analysing proper motions, we find one relevant kinematic group. This sparse object is relatively close (˜1 kpc), metal poor and is probably not only one of the oldest clusters (3 Gyr) within 1.5 kpc from the Sun but also one of the clusters located farthest from the disc, at an altitude of nearly -900 pc. That makes NGC 1252 the first open cluster that can be truly considered a high Galactic altitude OCR: an unusual object that may hint at a star formation event induced on a high Galactic altitude gas cloud. We also conclude that the variable TW Horologii and the blue straggler candidate HD 20286 are unlikely to be part of NGC 1252. NGC 1252 17 is identified as an unrelated, Population II cannonball star moving at about 400 km s-1.

  15. The old, metal-poor, anticentre open cluster Trumpler 5

    NASA Astrophysics Data System (ADS)

    Donati, P.; Cocozza, G.; Bragaglia, A.; Pancino, E.; Cantat-Gaudin, T.; Carrera, R.; Tosi, M.

    2015-01-01

    As part of a long-term programme, we analyse the evolutionary status and properties of the old and populous open cluster Trumpler 5 (Tr 5), located in the Galactic anticentre direction, almost on the Galactic plane. Tr 5 was observed with Wide Field Imager@MPG/ESO Telescope using the Bessel U, B, and V filters. The cluster parameters have been obtained using the synthetic colour-magnitude diagram (CMD) method, i.e. the direct comparison of the observational CMD with a library of synthetic CMDs generated with different stellar evolution sets (Padova, FRANEC, and FST). Age, reddening, and distance are derived through the synthetic CMD method using stellar evolutionary models with subsolar metallicity (Z = 0.004 or Z = 0.006). Additional spectroscopic observations with Ultraviolet VLT Echelle Spectrograph@Very Large Telescope of three red clump stars of the cluster were used to determine more robustly the chemical properties of the cluster. Our analysis shows that Tr 5 has subsolar metallicity, with [Fe/H] = -0.403 ± 0.006 dex (derived from spectroscopy), age between 2.9 and 4 Gyr (the lower age is found using stellar models without core overshooting), reddening E(B - V) in the range 0.60-0.66 mag complicated by a differential pattern (of the order of ˜±0.1 mag), and distance modulus (m - M)0 = 12.4 ± 0.1 mag.

  16. Issues involved in the atomic layer deposition of metals

    NASA Astrophysics Data System (ADS)

    Grubbs, Robert Kimes

    Auger Electron Spectroscopy (AES) was used to study the nucleation and growth of tungsten on aluminum oxide surfaces. Tungsten metal was deposited using Atomic Layer Deposition (ALD) techniques. ALD uses sequential surface reactions to deposit material with atomic layer control. W ALD is performed using sequential exposures of WF6 and Si2H6. The step-wise nature of W ALD allows nucleation studies to be performed by analyzing the W surface concentration after each ALD reaction. Nucleation and growth regions can be identified by quantifying the AES signal intensities from both the W surface and the Al2O3 substrate. W nucleation occurred in 3 ALD reaction cycles. The AES results yielded a nucleation rate of 1.0 A/ALD cycle and a growth rate of ≈3 A/ALD cycle. AES studies also explored the nucleation and growth of Al2O3 on W. Al2O3 nucleated in 1 ALD cycle giving a nucleation rate of 3.5 A/ALD cycle and a subsequent growth rate of 1.0 A/ALD cycle. Mass spectrometry was then used to study the ALD reaction chemistry of tungsten deposition. Because of the step-wise nature of the W ALD chemistry, each W ALD reaction could be studied independently. The gaseous mass products were identified from both the WF6 and Si2H6 reactions. H2, HF and SiF4 mass products were observed for the WF6 reaction. The Si2H6 reaction displayed a room temperature reaction and a 200°C reaction. Products from the room temperature Si2H6 reaction were H2 and SiF3H. The reaction at 200°C yielded only H2 as a reaction product. H2 desorption from the surface contributes to the 200°C Si2H6 reaction. AES was used to confirm that the gas phase reaction products are correlated with a change in the surface species. Atomic hydrogen reduction of metal halides and oganometallic compounds provides another method for depositing metals with atomic layer control. The quantity of atomic hydrogen necessary to perform this chemistry is critical to the metal ALD process. A thermocouple probe was constructed to

  17. Measuring Complementary Electronic Structure Properties of both Deposited and Gas Phase Clusters using STM, UPS, and PES: Size-Selected Clusters on Surfaces

    SciTech Connect

    Bowen, Kit H.

    2014-03-05

    In this project, we studied size-selected cluster interactions with surfaces, with other clusters on surfaces, and with external stimuli. These studies focused on mobility as a function of cluster size, surface morphologies as a function of composition and coverage, ion-induced modification and reactivity of clusters as a function of composition, the structural evolution of cluster cuboids culminating in the characterization of theoretically-predicted “baby crystal” clusters, and unusual fractal pattern formation due to deposition.

  18. Deposition of tungsten metal by an immersion process

    DOE PAGES

    Small, Leo J.; Brumbach, Michael T.; Clem, Paul G.; ...

    2017-03-23

    A new multi-step, solution-phase method for the spontaneous deposition of tungsten from a room temperature ethereal solution is reported. This immersion process relies on the deposition of a sacrificial zinc coating which is galvanically displaced by the ether-mediated reduction of oxophilic WCl6. Subsequent thermal treatment renders a crystalline, metallic tungsten film. The chemical evolution of the surface and formation of a complex intermediate tungsten species is characterized by X-ray diffraction, infrared spectroscopy, and X-ray photoelectron spectroscopy. Efficient metallic tungsten deposition is first characterized on a graphite substrate and then demonstrated on a functional carbon foam electrode. The resulting electrochemical performancemore » of the modified electrode is interrogated with the canonical aqueous ferricyanide system. A tungsten-coated carbon foam electrode showed that both electrode resistance and overall electrochemical cell resistance were reduced by 50%, resulting in a concomitant decrease in redox peak separation from 1.902 V to 0.783 V. Furthermore, this process promises voltage efficiency gains in electrodes for energy storage technologies and demonstrates the viability of a new route to tungsten coating for technologies and industries where high conductivity and chemical stability are paramount.« less

  19. Cotton fabrics with UV blocking properties through metal salts deposition

    NASA Astrophysics Data System (ADS)

    Emam, Hossam E.; Bechtold, Thomas

    2015-12-01

    Exposure to sunlight is important for human health as this increases the resistance to diverse pathogens, but the higher doses cause skin problems and diseases. Hence, wearing of sunlight protective fabrics displays a good solution for people working in open atmosphere. The current study offered quite simple and technically feasible ways to prepare good UV protection fabrics based on cotton. Metal salts including Zn, Cu and Ti were immobilized into cotton and oxidized cotton fabrics by using pad-dry-cure technique. Metal contents on fabrics were determined by AAS; the highest metal content was recorded for Cu-fabric and it was 360.6 mmol/kg after treatment of oxidized cotton with 0.5 M of copper nitrate. Ti contents on fabrics were ranged between 168.0 and 200.8 mmol/kg and it showed the lowest release as only 38.1-46.4% leached out fabrics after five laundry washings. Metal containing deposits were specified by scanning electron microscopy and energy dispersive X-ray spectroscopy. UV-transmission radiation over treated fabrics was measured and ultraviolet protection factor (UPF) was calculated. UPF was enhanced after treatment with Cu and Ti salts to be 11.6 and 14, respectively. After five washings, the amount of metal (Cu or Ti) retained indicates acceptable laundering durability.

  20. Aerosol chemical vapor deposition of metal oxide films

    DOEpatents

    Ott, K.C.; Kodas, T.T.

    1994-01-11

    A process of preparing a film of a multicomponent metal oxide including: forming an aerosol from a solution comprised of a suitable solvent and at least two precursor compounds capable of volatilizing at temperatures lower than the decomposition temperature of said precursor compounds; passing said aerosol in combination with a suitable oxygen-containing carrier gas into a heated zone, said heated zone having a temperature sufficient to evaporate the solvent and volatilize said precursor compounds; and passing said volatilized precursor compounds against the surface of a substrate, said substrate having a sufficient temperature to decompose said volatilized precursor compounds whereby metal atoms contained within said volatilized precursor compounds are deposited as a metal oxide film upon the substrate is disclosed. In addition, a coated article comprising a multicomponent metal oxide film conforming to the surface of a substrate selected from the group consisting of silicon, magnesium oxide, yttrium-stabilized zirconium oxide, sapphire, or lanthanum gallate, said multicomponent metal oxide film characterized as having a substantially uniform thickness upon said substrate.

  1. Critical Metals In Western Arctic Ocean Ferromanganese Mineral Deposits

    NASA Astrophysics Data System (ADS)

    Hein, J. R.; Spinardi, F.; Conrad, T. A.; Conrad, J. E.; Genetti, J.

    2013-12-01

    Little exploration for minerals has occurred in the Arctic Ocean due to ice cover and the remote location. Small deposits of seafloor massive sulfides that are rich in copper and zinc occur on Gakkel Ridge, which extends from Greenland to the Laptev Sea, and on Kolbeinsey and Mohns ridges, both located between Greenland and mainland Europe. However, rocks were recently collected by dredge along the western margin of the Canada Basin as part of the U.S. Extended Continental Shelf (ECS) program north of Alaska. Sample sites include steep escarpments on the Chukchi Borderland, a newly discovered seamount informally named Healy seamount, the southern part of Alpha-Mendeleev Ridge, and several basement outcrops in Nautilus Basin. These dredge hauls yielded three types of metal-rich mineralized deposits: ferromanganese crusts, ferromanganese nodules, and hydrothermal iron and manganese deposits. Chemical analyses of 43 crust and nodule samples show high contents of many critical metals needed for high-technology, green-technology, and energy and military applications, including cobalt (to 0.3 wt.%), vanadium (to 0.12 wt.%), zirconium (to 459 grams/tonne=ppm), molybdenum (to 453 g/t), the rare-earth elements (including scandium and yttrium; yttrium to 229 g/t), lithium (to 205 g/t), tungsten (to 64 g/t), and gallium (to 26 g/t). The metal contents of these Arctic Ocean crusts and nodules are comparable to those found throughout the global ocean, however, these Arctic Ocean samples are the first that have been found to be enriched in rare metal scandium. The metal contents of these samples indicate a diagenetic component. Crusts typically form by precipitation of metal oxides solely from seawater (hydrogenetic) onto rock surfaces producing a pavement, whereas nodules form by accretion of metal oxides, from both seawater and pore waters (diagenetic), around a nucleus on the surface of soft sediment. The best evidence for this diagenetic input to the crusts is that crusts

  2. Electronic Principles Governing the Stability and Reactivity of Ligated Metal and Silicon Encapsulated Transition Metal Clusters

    NASA Astrophysics Data System (ADS)

    Abreu, Marissa Baddick

    A thorough understanding of the underlying electronic principles guiding the stability and reactivity of clusters has direct implications for the identification of stable clusters for incorporation into clusters-assembled materials with tunable properties. This work explores the electronic principles governing the stability and reactivity of two types of clusters: ligated metal clusters and silicon encapsulated transition metal clusters. In the first case, the reactivity of iodine-protected aluminum clusters, Al13Ix - (x=0-4) and Al14Iy- (y=0-5), with the protic species methanol was studied. The symmetrical ground states of Al13Ix- showed no reactivity with methanol but reactivity was achieved in a higher energy isomer of Al 13I2- with iodines on adjacent aluminum atoms -- complementary Lewis acid-base active sites were induced on the opposite side of the cluster capable of breaking the O-H bond in methanol. Al 14Iy- (y=2-5) react with methanol, but only at the ligated adatom site. Reaction of methanol with Al14 - and Al14I- showed that ligation of the adatom was necessary for the reaction to occur there -- revealing the concept of a ligand-activated adatom. In the second case, the study focused heavily on CrSi12, a silicon encapsulated transition metal cluster whose stability and the reason for that stability has been debated heavily in the literature. Calculations of the energetic properties of CrSi n (n=6-16) revealed both CrSi12 and CrSi14 to have enhanced stability relative to other clusters; however CrSi12 lacks all the traditional markers of a magic cluster. Molecular orbital analysis of each of these clusters showed the CNFEG model to be inadequate in describing their stability. Because the 3dz2 orbital of Cr is unfilled in CrSi12, this cluster has only 16 effective valence electrons, meaning that the 18-electron rule is not applicable. The moderate stability of CrSi 12 can be accounted for by the crystal-field splitting of the 3d orbitals, which pushes the

  3. The chemical evolution of globular clusters - II. Metals and fluorine

    NASA Astrophysics Data System (ADS)

    Sánchez-Blázquez, P.; Marcolini, A.; Gibson, B. K.; Karakas, A. I.; Pilkington, K.; Calura, F.

    2012-01-01

    In the first paper of this series, we proposed a new framework in which to model the chemical evolution of globular clusters. This model is predicated upon the assumption that clusters form within an interstellar medium enriched locally by the ejecta of a single Type Ia supernova and varying numbers of asymptotic giant branch stars, superimposed on an ambient medium pre-enriched by low-metallicity Type II supernovae. Paper I was concerned with the application of this model to the observed abundances of several reactive elements and so-called non-metals for three classical intermediate-metallicity clusters, with the hallmark of the work being the successful recovery of many of their well-known elemental and isotopic abundance anomalies. Here, we expand upon our initial analysis by (i) applying the model to a much broader range of metallicities (from the factor of 3 explored in Paper I, to now a factor of ˜50; i.e. essentially, the full range of Galactic globular cluster abundances; and (ii) incorporating a broader suite of chemical species, including a number of iron-peak isotopes, heavier α-elements and fluorine. While allowing for an appropriate fine-tuning of the model input parameters, most empirical globular cluster abundance trends are reproduced; our model would suggest the need for a higher production of calcium, silicon and copper in low-metallicity (or so-called 'prompt') Type Ia supernovae than predicted in current stellar models in order to reproduce the observed trends in NGC 6752, and a factor of 2 reduction in carbon production from asymptotic giant branch stars to explain the observed trends between carbon and nitrogen. Observations of heavy-element isotopes produced primarily by Type Ia supernovae, including those of titanium, iron and nickel, could support/refute unequivocally our proposed framework, although currently the feasibility of the proposed observations is well beyond current instrumental capabilities. Hydrodynamical simulations would

  4. The Old, Super-Metal-Rich Open Cluster, NGC 6791

    NASA Astrophysics Data System (ADS)

    Boesgaard, Ann Merchant; Lum, Michael G. G.; Deliyannis, Constantine P.

    2015-08-01

    Stellar evolution and Galactic evolution have both been greatly advanced by the study of star clusters. In addition the elemental abundance results from clusters have revealed information about Galactic chemical evolution and nucleosynthesis. The cluster, NGC 6791, has a number of bizarre properties that make it especially interesting for comparative cluster studies. It is old (8.3 Gyr) yet metal-rich ([Fe/H] = +0.30). It has a heliocentric distance of 4 kpc and a galactic latitude of +11 degrees which makes it 1 kpc above the galactic plane. Its boxy orbit has a high eccentricity (~0.5) with a perigalactic distance of 3 kpc and an apogalactic distance of 10 kpc. The orbital period of ~130 Myr indicates that it has crossed the Galactic plane several times yet has remained as an intact cluster. We have determined abundances from high-resolution (R = 46,000) Keck/HIRES spectra of turn-off stars in this open cluster NGC 6791. We have a solid determination of [Fe/H] = +0.30 +/-0.02 from measurements of some 40 unblended, unsaturated lines of both Fe I and Fe II in eight turn-off stars. Our O abundances come from the O I triplet near 7774 Å and are corrected for small nLTE effects. We find consistent ratios of [O/Fe]n with a mean of -0.06 +/-0.02, indicating a single population of stars. Our results for the alpha elements [Mg/Fe], [Si/Fe], [Ca/Fe] and [Ti/Fe] are near solar and compare well with those of old, metal-rich field stars. The Fe-peak elements, Cr and Ni, have values of [Cr/Fe] = +0.05 +/-0.02 and [Ni/Fe] = +0.04 +/-0.01. Determinations of upper limits were found for Li by spectrum synthesis; this is consistent with the upper limits in this temperature range for turn-off/subgiant stars in the relatively old, super-metal-rich cluster NGC 6253. We speculate that no stars in NGC 6791 have retained the Li with which they formed.

  5. Direct Deposition of Metal (DDM) as a Repair Process for Metallic Military Parts

    DTIC Science & Technology

    2013-01-20

    welded are low carbon steel , nickel, titanium, and copper. Aluminum and cast iron alloys cannot be easily welded but altering the microstructure... Aluminum There are many possibilities for DDM fabrication with aluminum alloys and perhaps aluminum metal matrix composite materials FSW Tool...15 4340 Steel Deposit Mechanical Tests

  6. Ru and Os film deposition from metal carbonyls

    SciTech Connect

    Berry, A.D.; Brown, D.J.; Kaplan, R.; Cukauskas, E.J.

    1986-03-01

    Adherent, highly reflective films of Ru and Os have been deposited in vacuum on heated Si substrates by thermal decomposition of the pentacarbonyls Ru(CO)/sub 5/ and Os(CO)/sub 5/, at 150 and 200 /sup 0/C, respectively. Auger analysis after ion bombardment cleaning revealed nearly O-free surfaces, with slight C contamination which grew with exposure to the primary electron beam, thus making accurate determination of C content difficult. X-ray diffraction showed the films to be polycrystalline with the expected hexagonal close-packed structure, while measured resistivities were about a factor of 3 greater than bulk values. This method of depositing Ru and Os offers the advantages of simplicity, modest temperature requirement, and metallization of heated surfaces only.

  7. Volatile metal deposits on lunar soils: Relation to volcanism

    NASA Technical Reports Server (NTRS)

    Reed, G. W., Jr.; Allen, R. O., Jr.; Jovanovic, S.

    1977-01-01

    Parallel leaching and volatilization experiments conducted on lunar samples and similar experiments on sphalerite do not supply the information needed to resolve the question of the chemical nature of pb 204, Zn, Bi and Tl deposits on lunar soil surfaces. It is proposed that in Apollo 17 mare and terra soils and fractions of pb 204, Zn and Tl that are insoluble under mild, hot pH 5HNO3, leaching conditions and involatile at 600 C were originally surface deposits which became immobilized by migration into the silicate substrate or by chemisorption. Only Bi is predominantly indigenous. The implication is also that the soils over their respective times of evolution were exposed to heavy metal vapors or that an episodic exposure occurred after they had evolved. A sequence of events is proposed to account for orange 74220 and black 74001 glasses by lava fountaining and for soil 74241 as tephra from an explosive volcanic eruption.

  8. Protein-protected luminescent noble metal quantum clusters: an emerging trend in atomic cluster nanoscience

    PubMed Central

    Xavier, Paulrajpillai Lourdu; Chaudhari, Kamalesh; Baksi, Ananya; Pradeep, Thalappil

    2012-01-01

    Noble metal quantum clusters (NMQCs) are the missing link between isolated noble metal atoms and nanoparticles. NMQCs are sub-nanometer core sized clusters composed of a group of atoms, most often luminescent in the visible region, and possess intriguing photo-physical and chemical properties. A trend is observed in the use of ligands, ranging from phosphines to functional proteins, for the synthesis of NMQCs in the liquid phase. In this review, we briefly overview recent advancements in the synthesis of protein protected NMQCs with special emphasis on their structural and photo-physical properties. In view of the protein protection, coupled with direct synthesis and easy functionalization, this hybrid QC-protein system is expected to have numerous optical and bioimaging applications in the future, pointers in this direction are visible in the literature. PMID:22312454

  9. Protein-protected luminescent noble metal quantum clusters: an emerging trend in atomic cluster nanoscience.

    PubMed

    Xavier, Paulrajpillai Lourdu; Chaudhari, Kamalesh; Baksi, Ananya; Pradeep, Thalappil

    2012-01-01

    Noble metal quantum clusters (NMQCs) are the missing link between isolated noble metal atoms and nanoparticles. NMQCs are sub-nanometer core sized clusters composed of a group of atoms, most often luminescent in the visible region, and possess intriguing photo-physical and chemical properties. A trend is observed in the use of ligands, ranging from phosphines to functional proteins, for the synthesis of NMQCs in the liquid phase. In this review, we briefly overview recent advancements in the synthesis of protein protected NMQCs with special emphasis on their structural and photo-physical properties. In view of the protein protection, coupled with direct synthesis and easy functionalization, this hybrid QC-protein system is expected to have numerous optical and bioimaging applications in the future, pointers in this direction are visible in the literature.

  10. A uniform metallicity in the outskirts of massive, nearby galaxy clusters

    NASA Astrophysics Data System (ADS)

    Urban, O.; Werner, N.; Allen, S. W.; Simionescu, A.; Mantz, A.

    2017-10-01

    Suzaku measurements of a homogeneous metal distribution of Z ˜ 0.3 Solar in the outskirts of the nearby Perseus cluster suggest that chemical elements were deposited and mixed into the intergalactic medium before clusters formed, likely over 10 billion years ago. A key prediction of this early enrichment scenario is that the intracluster medium in all massive clusters should be uniformly enriched to a similar level. Here, we confirm this prediction by determining the iron abundances in the outskirts (r > 0.25r200) of a sample of 10 other nearby galaxy clusters observed with Suzaku for which robust measurements based on the Fe-K lines can be made. Across our sample, the iron abundances are consistent with a constant value, ZFe = 0.316 ± 0.012 Solar (χ2 = 28.85 for 25 degrees of freedom). This is remarkably similar to the measurements for the Perseus cluster of ZFe = 0.314 ± 0.012 Solar, using the Solar abundance scale of Asplund et al.

  11. A uniform metallicity in the outskirts of massive, nearby galaxy clusters

    DOE PAGES

    Urban, O.; Werner, N.; Allen, S. W.; ...

    2017-06-20

    Suzaku measurements of a homogeneous metal distribution of Z ~ 0:3 Solar in the outskirts of the nearby Perseus cluster suggest that chemical elements were deposited and mixed into the intergalactic medium before clusters formed, likely over 10 billion years ago. A key prediction of this early enrichment scenario is that the intracluster medium in all massive clusters should be uniformly enriched to a similar level. Here, we confirm this prediction by determining the iron abundances in the outskirts (r > 0:25r200) of a sample of ten other nearby galaxy clusters observed with Suzaku for which robust measurements based onmore » the Fe-K lines can be made. Across our sample the iron abundances are consistent with a constant value, ZFe = 0:316 ± 0:012 Solar (Χ2 = 28:85 for 25 degrees of freedom). This is remarkably similar to the measurements for the Perseus cluster of ZFe = 0:314±0:012 Solar, using the Solar abundance scale of Asplund et al. (2009).« less

  12. Deposition and Characterization of Thin Films on Metallic Substrates

    NASA Technical Reports Server (NTRS)

    Gatica, Jorge E.

    2005-01-01

    A CVD method was successfully developed to produce conversion coatings on aluminum alloys surfaces with reproducible results with a variety of precursors. A well defined protocol to prepare the precursor solutions formulated in a previous research was extended to other additives. It was demonstrated that solutions prepared following such a protocol could be used to systematically generate protective coatings onto aluminum surfaces. Experiments with a variety of formulations revealed that a refined deposition protocol yields reproducible conversion coatings of controlled composition. A preliminary correlation between solution formulations and successful precursors was derived. Coatings were tested for adhesion properties enhancement for commercial paints. A standard testing method was followed and clear trends were identified. Only one precursors was tested systematically. Anticipated work on other precursors should allow a better characterization of the effect of intermetallics on the production of conversion/protective coatings on metals and ceramics. The significance of this work was the practical demonstration that chemical vapor deposition (CVD) techniques can be used to systematically generate protective/conversion coating on non-ferrous surfaces. In order to become an effective approach to replace chromate-based pre- treatment processes, namely in the aerospace or automobile industry, the process parameters must be defined more precisely. Moreover, the feasibility of scale-up designs necessitates a more comprehensive characterization of the fluid flow, transport phenomena, and chemical kinetics interacting in the process. Kinetic characterization showed a significantly different effect of magnesium-based precursors when compared to iron-based precursors. Future work will concentrate on refining the process through computer simulations and further experimental studies on the effect of other transition metals to induce deposition of conversion/protective films

  13. Optimization of an ionized metal physical vapor deposition reactor

    SciTech Connect

    Lu, J.; Kushner, M.J.

    1998-12-31

    Conventional sputtering for microelectronic fabrication produces poorly collimated neutral atom fluxes. Ion fluxes, however, can be accelerated and collimated by using a conventional dc or rf substrate bias. Hence, magnetron ionized metal physical vapor deposition (IMPVD) can produce highly ionized metal fluxes that can be used to fill high-aspect-ratio vias and trenches in microelectronic devices. Hopwood and Qian have examined design issues in IMPVD systems. In this study, a Design of Experiment (DOE) has been numerically performed for an IMPVD reactor using an inductively coupled plasma and a capacitively biased substrate. Gas pressure, reactor geometry, ICP power, and number of inductive coils are the design variables. Uniformity, magnitude, and ionization fraction of the depositing fluxes are the response variables. The influence of the design variables on the response variables is examined, with the goals of obtaining high uniformity, high magnitude, and high ionization fraction of the depositing metal fluxes. The computational tool used in this study is the two-dimensional Hybrid Plasma Equipment Model (HPEM). The aspect ratio of the reactor (height/radius) ranges from 0.5 to 1.0, the gas pressure ranges from 10 to 40 mTorr, the ICP power ranges from 0.5 to 2.0 kW, and the number of ICP coils ranges from 2 to 6. It was found that: (a) uniformity maximizes at high aspect ratio, low power, and high pressure; (b) flux magnitude maximizes at low aspect ratio, high power, and low pressure; (c) ionization fraction maximizes at high aspect ratio, high power, and high pressure.

  14. FURTHER DEFINITION OF THE MASS-METALLICITY RELATION IN GLOBULAR CLUSTER SYSTEMS AROUND BRIGHTEST CLUSTER GALAXIES

    SciTech Connect

    Cockcroft, Robert; Harris, William E.; Wehner, Elizabeth M. H.; Whitmore, Bradley C.; Rothberg, Barry E-mail: harris@physics.mcmaster.ca E-mail: whitmore@stsci.edu

    2009-09-15

    We combine the globular cluster (GC) data for 15 brightest cluster galaxies and use this material to trace the mass-metallicity relations (MMRs) in their globular cluster systems (GCSs). This work extends previous studies which correlate the properties of the MMR with those of the host galaxy. Our combined data sets show a mean trend for the metal-poor subpopulation that corresponds to a scaling of heavy-element abundance with cluster mass Z {approx} M {sup 0.30{+-}}{sup 0.05}. No trend is seen for the metal-rich subpopulation which has a scaling relation that is consistent with zero. We also find that the scaling exponent is independent of the GCS specific frequency and host galaxy luminosity, except perhaps for dwarf galaxies. We present new photometry in (g',i') obtained with Gemini/GMOS for the GC populations around the southern giant ellipticals NGC 5193 and IC 4329. Both galaxies have rich cluster populations which show up as normal, bimodal sequences in the color-magnitude diagram. We test the observed MMRs and argue that they are statistically real, and not an artifact caused by the method we used. We also argue against asymmetric contamination causing the observed MMR as our mean results are no different from other contamination-free studies. Finally, we compare our method to the standard bimodal fitting method (KMM or RMIX) and find our results are consistent. Interpretation of these results is consistent with recent models for GC formation in which the MMR is determined by GC self-enrichment during their brief formation period.

  15. Vibrationally resolved anion photoelectron spectroscopy of metal clusters

    NASA Astrophysics Data System (ADS)

    Miller, Stephen R.

    Vibrationally resolved anion photoelectron spectroscopy of metal clusters Vibrationally resolved anion photoelectron spectroscopy (APES) and density functional theory (DFT) are applied to the study of structure and reactivity in small metal containing molecules. The studies described fall into two general categories: the study of bare metal clusters and the study of metal/organic ligand reactions. The current lack of spectroscopic data for small, bare gas-phase metal compounds makes the experimental study of such compounds important for understanding structure and bonding in open-shell metallic species. The heteronuclear diatomic anions MCu- (M = Cr, Mo) were prepared in a flowing afterglow ion-molecule reactor, and studied experimentally with APES. Anion and neutral vibrational frequencies and MCu electron affinities were obtained for both systems. The experiments were supplemented by DFT calculations. The combined use of experiment and theory allows for the assignment of both photoelectron spectra, including a reassignment of the CrCu ground state reported in the literature. Similarly, DFT was used to assign the anionic/neutral electronic states observed in the photoelectron spectra of Al3- and Al3O-. The study of partially ligated organometallic complexes offers a means of examining the interactions between metal atoms and individual ligand molecules. DFT was used to assign electronic states observed in the photoelectron spectra of NbC2H2-, NbC4H4 -NbC6H6- and VC6H 6-. Comparison of the NbnHn - (n = 2, 4, 6) spectra (obtained through the reaction of C2 H4 and Nb) with DFT results provides the first direct spectroscopic evidence of the conversion of ethylene to benzene by a gas phase metal atom. Experiments were used to probe the reactivity of Y with C2H 4 in an effort to examine the generality of the metal induced C 2H4 dehydrogenation/cyclization reactions. Some of the key products in the Y reactions were YC2H-, YC 2H2-, and YC6H5 -. However, the results

  16. An age difference of two billion years between a metal-rich and a metal-poor globular cluster.

    PubMed

    Hansen, B M S; Kalirai, J S; Anderson, J; Dotter, A; Richer, H B; Rich, R M; Shara, M M; Fahlman, G G; Hurley, J R; King, I R; Reitzel, D; Stetson, P B

    2013-08-01

    Globular clusters trace the formation history of the spheroidal components of our Galaxy and other galaxies, which represent the bulk of star formation over the history of the Universe. The clusters exhibit a range of metallicities (abundances of elements heavier than helium), with metal-poor clusters dominating the stellar halo of the Galaxy, and higher-metallicity clusters found within the inner Galaxy, associated with the stellar bulge, or the thick disk. Age differences between these clusters can indicate the sequence in which the components of the Galaxy formed, and in particular which clusters were formed outside the Galaxy and were later engulfed along with their original host galaxies, and which were formed within it. Here we report an absolute age of 9.9 ± 0.7 billion years (at 95 per cent confidence) for the metal-rich globular cluster 47 Tucanae, determined by modelling the properties of the cluster's white-dwarf cooling sequence. This is about two billion years younger than has been inferred for the metal-poor cluster NGC 6397 from the same models, and provides quantitative evidence that metal-rich clusters like 47 Tucanae formed later than metal-poor halo clusters like NGC 6397.

  17. Producing Magnesium Metallic Glass By Disintegrated Melt Deposition

    SciTech Connect

    Shanthi, M.; Gupta, M.; Jarfors, A. E. W.; Tan, M. J.

    2011-01-17

    Bulk metallic glasses are new class of engineering materials that exhibit high resistance to crystallization in the under cooled liquid state. The development of bulk metallic glasses of thickness 1cm or less has opened new doors for fundamental studies of both liquid state and glass transition previously not feasible in metallic materials. Moreover, bulk metallic glasses exhibit superior hardness, strength, specific strength, and elastic strain limit, along with good corrosion and wear resistance. Thus they are potential candidates in various sports, structural, engineering and medical applications. Among several BMGs investigated, magnesium-based BMGs have attracted considerable attention because of their low density and superior mechanical properties. The major drawback of this magnesium based BMGs is poor ductility. This can be overcome by the addition of ductile particles/reinforcement to the matrix. In this study, a new technique named disintegrated melt deposition technique was used to synthesize magnesium based BMGs. Rods of different sizes are cast using the current method. Mechanical characterization studies revealed that the amorphous rods produced by the current technique showed superior mechanical properties.

  18. Producing Magnesium Metallic Glass By Disintegrated Melt Deposition

    NASA Astrophysics Data System (ADS)

    Shanthi, M.; Gupta, M.; Jarfors, A. E. W.; Tan, M. J.

    2011-01-01

    Bulk metallic glasses are new class of engineering materials that exhibit high resistance to crystallization in the under cooled liquid state. The development of bulk metallic glasses of thickness 1cm or less has opened new doors for fundamental studies of both liquid state and glass transition previously not feasible in metallic materials. Moreover, bulk metallic glasses exhibit superior hardness, strength, specific strength, and elastic strain limit, along with good corrosion and wear resistance. Thus they are potential candidates in various sports, structural, engineering and medical applications. Among several BMGs investigated, magnesium-based BMGs have attracted considerable attention because of their low density and superior mechanical properties. The major drawback of this magnesium based BMGs is poor ductility. This can be overcome by the addition of ductile particles/reinforcement to the matrix. In this study, a new technique named disintegrated melt deposition technique was used to synthesize magnesium based BMGs. Rods of different sizes are cast using the current method. Mechanical characterization studies revealed that the amorphous rods produced by the current technique showed superior mechanical properties.

  19. Residual metallic contamination of transferred chemical vapor deposited graphene.

    PubMed

    Lupina, Grzegorz; Kitzmann, Julia; Costina, Ioan; Lukosius, Mindaugas; Wenger, Christian; Wolff, Andre; Vaziri, Sam; Östling, Mikael; Pasternak, Iwona; Krajewska, Aleksandra; Strupinski, Wlodek; Kataria, Satender; Gahoi, Amit; Lemme, Max C; Ruhl, Guenther; Zoth, Guenther; Luxenhofer, Oliver; Mehr, Wolfgang

    2015-05-26

    Integration of graphene with Si microelectronics is very appealing by offering a potentially broad range of new functionalities. New materials to be integrated with the Si platform must conform to stringent purity standards. Here, we investigate graphene layers grown on copper foils by chemical vapor deposition and transferred to silicon wafers by wet etching and electrochemical delamination methods with respect to residual submonolayer metallic contaminations. Regardless of the transfer method and associated cleaning scheme, time-of-flight secondary ion mass spectrometry and total reflection X-ray fluorescence measurements indicate that the graphene sheets are contaminated with residual metals (copper, iron) with a concentration exceeding 10(13) atoms/cm(2). These metal impurities appear to be partially mobile upon thermal treatment, as shown by depth profiling and reduction of the minority charge carrier diffusion length in the silicon substrate. As residual metallic impurities can significantly alter electronic and electrochemical properties of graphene and can severely impede the process of integration with silicon microelectronics, these results reveal that further progress in synthesis, handling, and cleaning of graphene is required to advance electronic and optoelectronic applications.

  20. Size-Selected Cluster Deposition Applied to Monopropellant Catalysts

    DTIC Science & Technology

    2006-03-01

    perfluorinated polymer tubing and plug valves were used to construct the hydrazine reservoir and pump-out system. The hydrazine vapor is metered into the UHV...Between each Irn+ deposition experiment, the film, together with all iridium and contaminants, was removed by 1 keV Ar+ peak temperature hydrazine

  1. Shell structure of magnesium and other divalent metal clusters

    SciTech Connect

    Diederich, Th.; Doeppner, T.; Fennel, Th.; Tiggesbaeumker, J.; Meiwes-Broer, K.-H.

    2005-08-15

    Clusters of the divalent metals magnesium, cadmium, and zinc have been grown in ultracold helium nanodroplets and studied by high-resolution mass spectrometry, with a special emphasis on magnesium. The mass spectra of all materials show similar characteristic features independent of the chosen ionization technique - i.e., electron impact ionization as well as nanosecond and femtosecond multiphoton excitation. In the lower-size range the abundance distributions can be explained by an electronic shell structure. The associated electron delocalization - i.e., metallic bonding - is found to set in at about N=20 atoms. For Mg{sub N} we have resolved crossings of electronic levels at the highest-occupied molecular orbital which result in additional magic numbers compared to the alkali metals: e.g., Mg{sub 40} with 80 electrons. This specific electronic shell structure is also present in the intensity pattern of doubly charged Mg{sub N}. For larger clusters (N{>=}92) a coexistence of electronic shell effects and geometrical packing is observed and a clear signature of icosahedral structure is present beyond N{>=}147.

  2. Diffusion and Interface Reaction of Cu/Si (100) Films Prepared by Cluster Beam Deposition

    NASA Astrophysics Data System (ADS)

    Gao, Xing-Xin; Jia, Yan-Hui; Li, Gong-Ping; Cho, Seong-Jin; Kim, Hee

    2011-03-01

    Cu thin films are deposited on Si (100) substrates by neutral cluster beams and ionized cluster beams. The atomic diffusion and interface reaction between the Cu films and the Si substrates of as-deposited and annealed at different temperatures (230°C, 450°C, 500°C and 600°C) are investigated by Rutherford backscattering spectrometry (RBS) and x-ray diffraction (XRD). Some significant results are obtained on the following aspects: (1) For the Cu/Si(100) samples prepared by neutral cluster beams and ionized cluster beams at Va = 0kV, atomic diffusion phenomena are observed clearly in the as-deposited samples. With the increase of annealing temperature, the interdiffusion becomes more apparent. However, the diffusion intensities of the RBS spectra of the Cu/Si(100) films using neutral cluster beams are always higher than that of the Cu/Si(100) films using ionized cluster beams at Va=0kV in the as-deposited and samples annealed at the same temperature. The compound of Cu3Si is observed in the as-deposited samples. (2) For the Cu/Si(100) samples prepared by ionized cluster beams at Va=1, 3, 5kV, atomic diffusion phenomena are observed in the as-deposited samples at Va=1, 5kV. For the samples prepared at Va = 3kV, the interdiffusion phenomenon is observed until 500°C annealing temperature. The reason for the difference is discussed.

  3. Statistical sampling of the distribution of uranium deposits using geologic/geographic clusters

    USGS Publications Warehouse

    Finch, W.I.; Grundy, W.D.; Pierson, C.T.

    1992-01-01

    The concept of geologic/geographic clusters was developed particularly to study grade and tonnage models for sandstone-type uranium deposits. A cluster is a grouping of mined as well as unmined uranium occurrences within an arbitrary area about 8 km across. A cluster is a statistical sample that will reflect accurately the distribution of uranium in large regions relative to various geologic and geographic features. The example of the Colorado Plateau Uranium Province reveals that only 3 percent of the total number of clusters is in the largest tonnage-size category, greater than 10,000 short tons U3O8, and that 80 percent of the clusters are hosted by Triassic and Jurassic rocks. The distributions of grade and tonnage for clusters in the Powder River Basin show a wide variation; the grade distribution is highly variable, reflecting a difference between roll-front deposits and concretionary deposits, and the Basin contains about half the number in the greater-than-10,000 tonnage-size class as does the Colorado Plateau, even though it is much smaller. The grade and tonnage models should prove useful in finding the richest and largest uranium deposits. ?? 1992 Oxford University Press.

  4. 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.

  5. Multiple populations in more metal-rich galactic globular clusters

    NASA Astrophysics Data System (ADS)

    Cordero, Maria J.

    In this thesis we present chemical abundances for bright stars in the intermediate metallicity globular cluster (GC) M5, and the relatively metal-rich GCs M71 and 47 Tuc with the goal of improving the understanding of chemical evolution in the metallicity regime sampled by these three GCs. The first chapter presents a brief historical overview in light element abundance variations in globular clusters. In the second chapter we present the results obtained for 47 Tuc, the most-metal rich cluster of my sample. 47 Tuc is an ideal target to study chemical evolution and GC formation in massive more metal-rich GCs since it is the closest massive GC. Chemical abundances for O, Na, Al, Si, Ca, Ti, Fe, Ni, La, and Eu were determined for 164 red giant branch (RGB) stars in 47 Tuc using spectra obtained with both the Hydra multi-fiber spectrograph at the Blanco 4-m telescope and the FLAMES multi-object spectrograph at the ESO Very Large Telescope. The average [Fe/H]= --0.79+/-0.09 dex is consistent with literature values, as well as over-abundances of alpha-elements ([alpha/Fe] ~ 0.3 dex). The n-capture process elements indicate that 47 Tuc is r-process dominated ([Eu/La]=+0.24), and the light elements O, Na, and Al exhibit star-to-star variations. The Na-O anti-correlation, a signature typically seen in Galactic GCs, is present in 47 Tuc, and extends to include a small number of stars with [O/Fe] ~ --0.5. Additionally, the [O/Na] ratios of our sample reveal that the cluster stars can be separated into three distinct populations. A KS-test demonstrates that the O-poor/Na-rich stars are more centrally concentrated than the O-rich/Na-poor stars. The observed number and radial distribution of 47 Tuc's stellar populations, as distinguished by their light element composition, agrees closely with the results obtained from photometric data. We do not find evidence supporting a strong Na-Al correlation in 47 Tuc, which is consistent with current models of AGB nucleosynthesis yields

  6. Oligomeric rare-earth metal cluster complexes with endohedral transition metal atoms

    SciTech Connect

    Steinberg, Simon; Zimmermann, Sina; Brühmann, Matthias; Meyer, Eva; Rustige, Christian; Wolberg, Marike; Daub, Kathrin; Bell, Thomas; Meyer, Gerd

    2014-11-15

    Comproportionation reactions of rare-earth metal trihalides (RX{sub 3}) with the respective rare-earth metals (R) and transition metals (T) led to the formation of 22 oligomeric R cluster halides encapsulating T, in 19 cases for the first time. The structures of these compounds were determined by single-crystal X-ray diffraction and are composed of trimers ((T{sub 3}R{sub 11})X{sub 15}-type, P6{sub 3}/m), tetramers ((T{sub 4}R{sub 16})X{sub 28}(R{sub 4}) (P-43m), (T{sub 4}R{sub 16})X{sub 20} (P4{sub 2}/nnm), (T{sub 4}R{sub 16})X{sub 24}(RX{sub 3}){sub 4} (I4{sub 1}/a) and (T{sub 4}R{sub 16})X{sub 23} (C2/m) types of structure) and pentamers ((Ru{sub 5}La{sub 14}){sub 2}Br{sub 39}, Cc) of (TR{sub r}){sub n} (n=2–5) clusters. These oligomers are further enveloped by inner (X{sup i}) as well as outer (X{sup a}) halido ligands, which possess diverse functionalities and interconnect like oligomers through i–i, i–a and/or a–i bridges. The general features of the crystal structures for these new compounds are discussed and compared to literature entries as well as different structure types with oligomeric T centered R clusters. Dimers and tetramers originating from the aggregation of (TR{sub 6}) octahedra via common edges are more frequent than trimers and pentamers, in which the (TR{sub r}) clusters share common faces. - Graphical abstract: Rare earth-metal cluster complexes with endohedral transition metal atoms (TR{sub 6}) may connect via common edges or faces to form dimers, trimers, tetramers and pentamers of which the tetramers are the most prolific. Packing effects and electron counts play an important role. - Highlights: • Rare-earth metal cluster complexes encapsulate transition metal atoms. • Oligomers are built via connection of octahedral clusters via common edges or faces. • Dimers through pentamers with closed structures are known. • Tetramers including a tetrahedron of endohedral atoms are the most prolific.

  7. The Sound Parameter Effect in Metal-Rich Globular Clusters

    NASA Technical Reports Server (NTRS)

    Hall, D. K

    1998-01-01

    Recent Hubble Space Telescope observations have found that the horizontal branches (HBs) in the metal-rich globular clusters NGC 6388 and NGC 6441 slope upward with decreasing B - V. Such a slope is not predicted by canonical HB models and cannot be produced by either a greater cluster age or enhanced mass loss along the red giant branch (RGB). The peculiar HB morphology in these clusters may provide an important clue for understanding the second-parameter effect. We have carried out extensive evolutionary calculations and numerical simulations in order to explore three noncanonical scenarios for explaining the sloped HBs in NGC 6388 and NGC 6441: (1) a high cluster helium abundance scenario, in which the HB evolution is characterized by long blue loops; (2) a rotation scenario, in which internal rotation during the RGB phase increases the HB core mass; and (3) a helium-mixing scenario, in which deep mixing on the RGB enhances the envelope helium abundance. All of these scenarios predict sloped HBs with anomalously bright RR Lyrae variables. We compare this prediction with the properties of the two known RR Lyrae variables in NGC 6388. Additional observational tests of these scenarios are suggested.

  8. Characteristic properties of the Casimir free energy for metal films deposited on metallic plates

    NASA Astrophysics Data System (ADS)

    Klimchitskaya, G. L.; Mostepanenko, V. M.

    2016-04-01

    The Casimir free energy and pressure of thin metal films deposited on metallic plates are considered using the Lifshitz theory and the Drude and plasma model approaches to the role of conduction electrons. The bound electrons are taken into account by using the complete optical data of film and plate metals. It is shown that for films of several tens of nanometers thickness the Casimir free energy and pressure calculated using these approaches differ by hundreds and thousands percent and can be easily discriminated experimentally. According to our results, the free energy of a metal film does not vanish in the limiting case of ideal metal if the Drude model approach is used in contradiction with the fact that the fluctuating field cannot penetrate in its interior. Numerical computations of the Casimir free energy and pressure of Ag and Au films deposited on Cu and Al plates have been performed using both theoretical approaches. It is shown that the free energy of a film can be both negative and positive depending on the metals used. For a Au film on a Ag plate and vice versa the Casimir energy of a film changes its sign with increasing film thickness. Applications of the obtained results for resolving the Casimir puzzle and the problem of stability of thin films are discussed.

  9. The electronic structure of free aluminum clusters: Metallicity and plasmons

    SciTech Connect

    Andersson, Tomas; Zhang Chaofan; Svensson, Svante; Maartensson, Nils; Bjoerneholm, Olle; Tchaplyguine, Maxim

    2012-05-28

    The electronic structure of free aluminum clusters with {approx}3-4 nm radius has been investigated using synchrotron radiation-based photoelectron and Auger electron spectroscopy. A beam of free clusters has been produced using a gas-aggregation source. The 2p core level and the valence band have been probed. Photoelectron energy-loss features corresponding to both bulk and surface plasmon excitation following photoionization of the 2p level have been observed, and the excitation energies have been derived. In contrast to some expectations, the loss features have been detected at energies very close to those of the macroscopic solid. The results are discussed from the point of view of metallic properties in nanoparticles with a finite number of constituent atoms.

  10. Mixed-metal chalcogenide tetrahedral clusters with an exo-polyhedral metal fragment.

    PubMed

    Yuvaraj, K; Roy, Dipak Kumar; Anju, V P; Mondal, Bijnaneswar; Varghese, Babu; Ghosh, Sundargopal

    2014-12-07

    The reaction of metal carbonyl compounds with group 6 and 8 metallaboranes led us to report the synthesis and structural characterization of several novel mixed-metal chalcogenide tetrahedral clusters. Thermolysis of arachno-[(Cp*RuCO)2B2H6], 1, and [Os3(CO)12] in the presence of 2-methylthiophene yielded [Cp*Ru(CO)2(μ-H){Os3(CO)9}S], 3, and [Cp*Ru(μ-H){Os3(CO)11}], 4. In a similar fashion, the reaction of [(Cp*Mo)2B5H9], 2, with [Ru3(CO)12] and 2-methylthiophene yielded [Cp*Ru(CO)2(μ-H){Ru3(CO)9}S], 5, and conjuncto-[(Cp*Mo)2B5H8(μ-H){Ru3(CO)9}S], 6. Both compounds 3 and 5 can be described as 50-cve (cluster valence electron) mixed-metal chalcogenide clusters, in which a sulfur atom replaces one of the vertices of the tetrahedral core. Compounds 3 and 5 possess a [M3S] tetrahedral core, in which the sulfur is attached to an exo-metal fragment, unique in the [M3S] metal chalcogenide tetrahedral arrangements. All the compounds have been characterized by mass spectrometry, IR, and (1)H, (11)B and (13)C NMR spectroscopy in solution, and the solid state structures were unequivocally established by crystallographic analysis of compounds 3, 5 and 6.

  11. Metal thiolate clusters in cobalt(II)-metallothionein.

    PubMed

    Vasák, M; Kägi, J H

    1981-11-01

    Rabbit liver metallothionein-1 in which all seven metal-binding sites are occupied by cobalt(II) exhibits spectral features typical of tetrathiolate coordination with approximate Td microsymmetry [Vasák, M. (1980) J. Am. Chem. Soc. 102, 3953-3955]. With a total of 20 cysteine residues per molecule, this mode of metal binding implies that some of the thiolate ligands are shared by neighboring Co(II) ions, resulting in clustered structures. In this study, evidence for the existence of thiolate-linked Co(II) clusters is presented and their mode of formation is explored by comparing the optical and magnetic properties of forms of Co(II)-metallothionein containing 1-7 equivalents of Co(II). Preparations with up to 4 Co(II) equivalents display electronic spectra in the d-d and charge-transfer regions that resemble those of isolated tetrahedral Co(II)-tetrathiolate complexes. Upon binding of more than four Co(II) ions, however, the spectrum changes progressively and approaches in the fully saturated Co(II)-metallothionein an absorption profile similar to that of crystallographically defined model (Co)II-tetrathiolate clusters [Dance, I. G. (1979) J. Am. Chem. Soc. 101, 6264-6273]. These effects are closely paralleled by changes in the ESR spectrum. Above 4 Co(II) equivalents per thionein, the ESR signal at gx approximately 5.9 measured at 4 K decreases progressively in intensity, until in the fully occupied protein the complex is nearly diamagnetic. These changes, which were confirmed by measurements of paramagnetic susceptibility, establish the existence of Co(II) thiolate clusters in Co(II)-metallothionein. The loss of paramagnetism reflects most likely antiferromagnetic coupling of neighboring Co(II) ions brought about by a superexchange mechanism via the thiolate bridging ligands.

  12. Metal thiolate clusters in cobalt(II)-metallothionein.

    PubMed Central

    Vasák, M; Kägi, J H

    1981-01-01

    Rabbit liver metallothionein-1 in which all seven metal-binding sites are occupied by cobalt(II) exhibits spectral features typical of tetrathiolate coordination with approximate Td microsymmetry [Vasák, M. (1980) J. Am. Chem. Soc. 102, 3953-3955]. With a total of 20 cysteine residues per molecule, this mode of metal binding implies that some of the thiolate ligands are shared by neighboring Co(II) ions, resulting in clustered structures. In this study, evidence for the existence of thiolate-linked Co(II) clusters is presented and their mode of formation is explored by comparing the optical and magnetic properties of forms of Co(II)-metallothionein containing 1-7 equivalents of Co(II). Preparations with up to 4 Co(II) equivalents display electronic spectra in the d-d and charge-transfer regions that resemble those of isolated tetrahedral Co(II)-tetrathiolate complexes. Upon binding of more than four Co(II) ions, however, the spectrum changes progressively and approaches in the fully saturated Co(II)-metallothionein an absorption profile similar to that of crystallographically defined model (Co)II-tetrathiolate clusters [Dance, I. G. (1979) J. Am. Chem. Soc. 101, 6264-6273]. These effects are closely paralleled by changes in the ESR spectrum. Above 4 Co(II) equivalents per thionein, the ESR signal at gx approximately 5.9 measured at 4 K decreases progressively in intensity, until in the fully occupied protein the complex is nearly diamagnetic. These changes, which were confirmed by measurements of paramagnetic susceptibility, establish the existence of Co(II) thiolate clusters in Co(II)-metallothionein. The loss of paramagnetism reflects most likely antiferromagnetic coupling of neighboring Co(II) ions brought about by a superexchange mechanism via the thiolate bridging ligands. PMID:6273885

  13. Analysis and assessment on heavy metal sources in the coastal soils developed from alluvial deposits using multivariate statistical methods.

    PubMed

    Li, Jinling; He, Ming; Han, Wei; Gu, Yifan

    2009-05-30

    An investigation on heavy metal sources, i.e., Cu, Zn, Ni, Pb, Cr, and Cd in the coastal soils of Shanghai, China, was conducted using multivariate statistical methods (principal component analysis, clustering analysis, and correlation analysis). All the results of the multivariate analysis showed that: (i) Cu, Ni, Pb, and Cd had anthropogenic sources (e.g., overuse of chemical fertilizers and pesticides, industrial and municipal discharges, animal wastes, sewage irrigation, etc.); (ii) Zn and Cr were associated with parent materials and therefore had natural sources (e.g., the weathering process of parent materials and subsequent pedo-genesis due to the alluvial deposits). The effect of heavy metals in the soils was greatly affected by soil formation, atmospheric deposition, and human activities. These findings provided essential information on the possible sources of heavy metals, which would contribute to the monitoring and assessment process of agricultural soils in worldwide regions.

  14. Volatile metal deposits on lunar soils - Relation to volcanism

    NASA Technical Reports Server (NTRS)

    Reed, G. W., Jr.; Jovanovic, S.; Allen, R. O., Jr.

    1977-01-01

    Parallel leaching and volatilization experiments conducted on lunar samples and similar experiments on sphalerite do not supply the information needed to resolve the question of the chemical nature of Pb-204, Zn, Bi, and Tl deposits on lunar soil surfaces. It is proposed that in Apollo 17 mare and terra soils the fractions of Pb-204, Zn, and Tl that are insoluble under mild, hot pH 5 HNO3, leaching conditions and involatile at 600 C were originally surface deposits which became immobilized by migration into the silicate substrate or by chemisorption. Most of the Bi does not seem to be the result of such a deposit. The implication is also that the soils, over their respective times of evolution, were exposed to heavy metal vapors or that an episodic exposure occurred after they had evolved. A sequence of events is proposed to account for orange 74220 and black 74001 glasses by lava fountaining and for soil 74241 as tephra from an explosive volcanic eruption.

  15. Volatile metal deposits on lunar soils - Relation to volcanism

    NASA Technical Reports Server (NTRS)

    Reed, G. W., Jr.; Jovanovic, S.; Allen, R. O., Jr.

    1977-01-01

    Parallel leaching and volatilization experiments conducted on lunar samples and similar experiments on sphalerite do not supply the information needed to resolve the question of the chemical nature of Pb-204, Zn, Bi, and Tl deposits on lunar soil surfaces. It is proposed that in Apollo 17 mare and terra soils the fractions of Pb-204, Zn, and Tl that are insoluble under mild, hot pH 5 HNO3, leaching conditions and involatile at 600 C were originally surface deposits which became immobilized by migration into the silicate substrate or by chemisorption. Most of the Bi does not seem to be the result of such a deposit. The implication is also that the soils, over their respective times of evolution, were exposed to heavy metal vapors or that an episodic exposure occurred after they had evolved. A sequence of events is proposed to account for orange 74220 and black 74001 glasses by lava fountaining and for soil 74241 as tephra from an explosive volcanic eruption.

  16. Superatoms and Metal-Semiconductor Motifs for Cluster Materials

    SciTech Connect

    Castleman, A. W.

    2013-10-11

    A molecular understanding of catalysis and catalytically active materials is of fundamental importance in designing new substances for applications in energy and fuels. We have performed reactivity studies and ultrafast ionization and coulomb explosion studies on a variety of catalytically-relevant materials, including transition metal oxides of Fe, Co, Ni, Cu, Ti, V, Nb, and Ta. We demonstrate that differences in charge state, geometry, and elemental composition of clusters of such materials determine chemical reactivity and ionization behavior, crucial steps in improving performance of catalysts.

  17. Metallic Conductive Nanowires Elaborated by PVD Metal Deposition on Suspended DNA Bundles.

    PubMed

    Brun, Christophe; Elchinger, Pierre-Henri; Nonglaton, Guillaume; Tidiane-Diagne, Cheikh; Tiron, Raluca; Thuaire, Aurélie; Gasparutto, Didier; Baillin, Xavier

    2017-09-01

    Metallic conductive nanowires (NWs) with DNA bundle core are achieved, thanks to an original process relying on double-stranded DNA alignment and physical vapor deposition (PVD) metallization steps involving a silicon substrate. First, bundles of DNA are suspended with a repeatable process between 2 µm high parallel electrodes with separating gaps ranging from 800 nm to 2 µm. The process consists in the drop deposition of a DNA lambda-phage solution on the electrodes followed by a naturally evaporation step. The deposition process is controlled by the DNA concentration within the buffer solution, the drop volume, and the electrode hydrophobicity. The suspended bundles are finally metallized with various thicknesses of titanium and gold by a PVD e-beam evaporation process. The achieved NWs have a width ranging from a few nanometers up to 100 nm. The electrical behavior of the achieved 60 and 80 nm width metallic NWs is shown to be Ohmic and their intrinsic resistance is estimated according to different geometrical models of the NW section area. For the 80 nm width NWs, a resistance of about few ohms is established, opening exploration fields for applications in microelectronics. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. On the origin of metal homogeneities in globular clusters

    NASA Technical Reports Server (NTRS)

    Murray, Stephen D.; Lin, Douglas N. C.

    1990-01-01

    Various transport processes which may have affected the chemical homogeneity in protocluster clouds are examined. It is shown that the characteristic diffusion time scale associated with collisions between grains and gas atoms is considerably longer than that on which star formation is expected to occur. Collisions between large grains and gas atoms lead to mass segregation and metallicity gradients on a time scale comparable to the crossing time of the clusters in the Galaxy. One possible mechanism for inducing and maintaining chemical homogeneity is turbulent diffusion in the clouds. The mixing time scale required in this case is comparable to several internal dynamical time scales, longer than the evolutionary time scale of the most massive stars, and shorter than the Galactic orbital time scale of the clouds. Thus, metals in presently observed stars probably did not originate from upper main-sequence stars of a coeval generation.

  19. Zintl cluster chemistry in the alkali-metal-gallium systems

    SciTech Connect

    Henning, Robert

    1998-03-27

    Previous research into the alkali-metal-gallium systems has revealed a large variety of networked gallium deltahedra. The clusters are analogues to borane clusters and follow the same electronic requirements of 2n+2 skeletal electrons for closo-deltahedra. This work has focused on compounds that do not follow the typical electron counting rules. The first isolated gallium cluster was found in Cs8Ga11. The geometry of the Ga117- unit is not deltahedral but can be described as a penta-capped trigonal prism. The reduction of the charge from a closo-Ga1113- to Ga117- is believed to be the driving force of the distortion. The compound is paramagnetic because of an extra electron but incorporation of a halide atom into the structure captures the unpaired electron and forms a diamagnetic compound. A second isolated cluster has been found in Na10Ga10Ni where the tetra-capped trigonal prismatic gallium is centered by nickel. Stabilization of the cluster occurs through Ni-Ga bonding. A simple two-dimensional network occurs in the binary K2Ga3 Octahedra are connected through four waist atoms to form a layered structure with the potassium atoms sitting between the layers. Na30.5Ga60-xAgx is nonstoichiometric and needs only a small amount of silver to form (x ~ 2-6). The structure is composed of three different clusters which are interconnected to form a three-dimensional structure. The RbGa3-xAux system is also nonstoichiometric with a three-dimensional structure composed of Ga8 dodecahedra and four-bonded gallium atoms. Unlike Na30.5Ga60-xAgx, the RbGa3 binary is also stable. The binary is formally a Zintl phase but the ternary is not. Some chemistry in the alkali-metal-indium system also has been explored. A new potassium-indium binary

  20. Single target sputter deposition of alloy nanoparticles with adjustable composition via a gas aggregation cluster source

    NASA Astrophysics Data System (ADS)

    Vahl, Alexander; Strobel, Julian; Reichstein, Wiebke; Polonskyi, Oleksandr; Strunskus, Thomas; Kienle, Lorenz; Faupel, Franz

    2017-04-01

    Alloy nanoparticles with variable compositions add a new dimension to nanoscience and have many applications. Here we suggest a novel approach for the fabrication of variable composition alloy nanoparticles that is based on a Haberland type gas aggregation cluster source with a custom-made multicomponent target for magnetron sputtering. The approach, which was demonstrated here for gold-rich AgAu nanoparticles, combines a narrow nanoparticle size distribution with in operando variation of composition via the gas pressure as well as highly efficient usage of target material. The latter is particularly attractive for precious metals. Varying argon pressure during deposition, we achieved in operando changes of AgAu alloy nanoparticle composition of more than 13 at%. The alloy nanoparticles were characterized by x-ray photoelectron spectroscopy and energy dispersive x-ray spectroscopy. The characteristic plasmon resonances of multilayer nanoparticle composites were analyzed by UV-vis spectroscopy. Tuning of the number of particles per unit area (particle densities) within individual layers showed an additional degree of freedom to tailor the optical properties of multilayer nanocomposites. By extension of this technique to more complex systems, the presented results are expected to encourage and simplify further research based on plasmonic multi-element nanoparticles. The present method is by no means restricted to plasmonics or nanoparticle based applications, but is also highly relevant for conventional magnetron sputtering of alloys and can be extended to in operando control of alloy concentration by magnetic field.

  1. Single target sputter deposition of alloy nanoparticles with adjustable composition via a gas aggregation cluster source.

    PubMed

    Vahl, Alexander; Strobel, Julian; Reichstein, Wiebke; Polonskyi, Oleksandr; Strunskus, Thomas; Kienle, Lorenz; Faupel, Franz

    2017-04-28

    Alloy nanoparticles with variable compositions add a new dimension to nanoscience and have many applications. Here we suggest a novel approach for the fabrication of variable composition alloy nanoparticles that is based on a Haberland type gas aggregation cluster source with a custom-made multicomponent target for magnetron sputtering. The approach, which was demonstrated here for gold-rich AgAu nanoparticles, combines a narrow nanoparticle size distribution with in operando variation of composition via the gas pressure as well as highly efficient usage of target material. The latter is particularly attractive for precious metals. Varying argon pressure during deposition, we achieved in operando changes of AgAu alloy nanoparticle composition of more than 13 at%. The alloy nanoparticles were characterized by x-ray photoelectron spectroscopy and energy dispersive x-ray spectroscopy. The characteristic plasmon resonances of multilayer nanoparticle composites were analyzed by UV-vis spectroscopy. Tuning of the number of particles per unit area (particle densities) within individual layers showed an additional degree of freedom to tailor the optical properties of multilayer nanocomposites. By extension of this technique to more complex systems, the presented results are expected to encourage and simplify further research based on plasmonic multi-element nanoparticles. The present method is by no means restricted to plasmonics or nanoparticle based applications, but is also highly relevant for conventional magnetron sputtering of alloys and can be extended to in operando control of alloy concentration by magnetic field.

  2. Nanomanufacturing of titania interfaces with controlled structural and functional properties by supersonic cluster beam deposition

    SciTech Connect

    Podestà, Alessandro E-mail: pmilani@mi.infn.it; Borghi, Francesca; Indrieri, Marco; Bovio, Simone; Piazzoni, Claudio; Milani, Paolo E-mail: pmilani@mi.infn.it

    2015-12-21

    Great emphasis is placed on the development of integrated approaches for the synthesis and the characterization of ad hoc nanostructured platforms, to be used as templates with controlled morphology and chemical properties for the investigation of specific phenomena of great relevance in interdisciplinary fields such as biotechnology, medicine, and advanced materials. Here, we discuss the crucial role and the advantages of thin film deposition strategies based on cluster-assembling from supersonic cluster beams. We select cluster-assembled nanostructured titania (ns-TiO{sub 2}) as a case study to demonstrate that accurate control over morphological parameters can be routinely achieved, and consequently, over several relevant interfacial properties and phenomena, like surface charging in a liquid electrolyte, and proteins and nanoparticles adsorption. In particular, we show that the very good control of nanoscale morphology is obtained by taking advantage of simple scaling laws governing the ballistic deposition regime of low-energy, mass-dispersed clusters with reduced surface mobility.

  3. Nanomanufacturing of titania interfaces with controlled structural and functional properties by supersonic cluster beam deposition

    NASA Astrophysics Data System (ADS)

    Podestà, Alessandro; Borghi, Francesca; Indrieri, Marco; Bovio, Simone; Piazzoni, Claudio; Milani, Paolo

    2015-12-01

    Great emphasis is placed on the development of integrated approaches for the synthesis and the characterization of ad hoc nanostructured platforms, to be used as templates with controlled morphology and chemical properties for the investigation of specific phenomena of great relevance in interdisciplinary fields such as biotechnology, medicine, and advanced materials. Here, we discuss the crucial role and the advantages of thin film deposition strategies based on cluster-assembling from supersonic cluster beams. We select cluster-assembled nanostructured titania (ns-TiO2) as a case study to demonstrate that accurate control over morphological parameters can be routinely achieved, and consequently, over several relevant interfacial properties and phenomena, like surface charging in a liquid electrolyte, and proteins and nanoparticles adsorption. In particular, we show that the very good control of nanoscale morphology is obtained by taking advantage of simple scaling laws governing the ballistic deposition regime of low-energy, mass-dispersed clusters with reduced surface mobility.

  4. Photocatalytic activity of nanostructured TiO2 films produced by supersonic cluster beam deposition

    NASA Astrophysics Data System (ADS)

    Della Foglia, Flavio; Losco, Tonia; Piseri, Paolo; Milani, Paolo; Selli, Elena

    2009-08-01

    The photocatalytic activity of thin, nanostructured films of titanium dioxide, synthesized by supersonic cluster beam deposition (SCBD) from the gas phase, has been investigated employing the photodegradation of salicylic acid as test reaction. Because of the low deposition energy, the so-deposited highly porous TiO2 films are composed of nanoparticles maintaining their original properties in the film, which can be fully controlled by tuning the deposition and post-deposition treatment conditions. A systematic investigation on the evolution of light absorption properties and photoactivity of the films in relation to their morphology, determined by AFM analysis, and phase composition, determined by Raman spectroscopy, has been performed. The absorption and photocatalytic activity of the nanostructured films in the visible region could be enhanced either through post-deposition annealing treatment in ammonia containing atmosphere or employing mild oxidation conditions, followed by annealing in N2 at 600 °C.

  5. Optical properties of silicon clusters deposited on the basal plane of graphite

    NASA Astrophysics Data System (ADS)

    Dinh, L. N.; Chase, L. L.; Balooch, M.; Terminello, L. J.; Tench, R. J.; Wooten, F.

    1994-04-01

    Laser ablation was used to deposit of silicon on highly oriented pyrolytic graphite surfaces in an ultra high-vacuum environment equipped with Auger electron spectroscopy (AES), scanning tunneling microscopy (STM) and luminescence spectroscopy. For deposition of up to several monolayers, post annealing produced silicon clusters, whose size distribution was determined vs annealing time and temperature using STM. Pure silicon clusters ranging from 1 to 10 nm showed no detectable photoluminescence in visible range. Exposure to oxygen at 10(exp -6) Torr and for up to 8 hours showed adsorption on the surface of the clusters without silicon oxide formation and no detectable luminescence. Hydrogen termination of these clusters was accomplished by exposing them to atomic hydrogen beam but did not result in any photoluminescence. Prolonged exposure of these clusters to ambient air, however, resulted in strong photoluminescence spectra with color ranging from red to greenish-blue depending on average cluster size. Auger electron spectra revealed the existence of partially oxidized silicon clusters. This luminescence could be due to either an oxide phase or to changes in electronic structure of the clusters as a result of quantum confinement effect.

  6. Oligomeric rare-earth metal cluster complexes with endohedral transition metal atoms

    NASA Astrophysics Data System (ADS)

    Steinberg, Simon; Zimmermann, Sina; Brühmann, Matthias; Meyer, Eva; Rustige, Christian; Wolberg, Marike; Daub, Kathrin; Bell, Thomas; Meyer, Gerd

    2014-11-01

    Comproportionation reactions of rare-earth metal trihalides (RX3) with the respective rare-earth metals (R) and transition metals (T) led to the formation of 22 oligomeric R cluster halides encapsulating T, in 19 cases for the first time. The structures of these compounds were determined by single-crystal X-ray diffraction and are composed of trimers ({T3R11}X15-type, P63/m), tetramers ({T4R16}X28{R4} (P-43m), {T4R16}X20 (P42/nnm), {T4R16}X24(RX3)4 (I41/a) and {T4R16}X23 (C2/m) types of structure) and pentamers ({Ru5La14}2Br39, Cc) of {TRr}n (n=2-5) clusters. These oligomers are further enveloped by inner (Xi) as well as outer (Xa) halido ligands, which possess diverse functionalities and interconnect like oligomers through i-i, i-a and/or a-i bridges. The general features of the crystal structures for these new compounds are discussed and compared to literature entries as well as different structure types with oligomeric T centered R clusters. Dimers and tetramers originating from the aggregation of {TR6} octahedra via common edges are more frequent than trimers and pentamers, in which the {TRr} clusters share common faces.

  7. Tuning aromaticity in trigonal alkaline earth metal clusters and their alkali metal salts.

    PubMed

    Jiménez-Halla, J Oscar C; Matito, Eduard; Blancafort, Lluís; Robles, Juvencio; Solà, Miquel

    2009-12-01

    In this work, we analyze the geometry and electronic structure of the [X(n)M(3)](n-2) species (M = Be, Mg, and Ca; X = Li, Na, and K; n = 0, 1, and 2), with special emphasis on the electron delocalization properties and aromaticity of the cyclo-[M(3)](2-) unit. The cyclo-[M(3)](2-) ring is held together through a three-center two-electron bond of sigma-character. Interestingly, the interaction of these small clusters with alkali metals stabilizes the cyclo-[M(3)](2-) ring and leads to a change from sigma-aromaticity in the bound state of the cyclo-[M(3)](2-) to pi-aromaticity in the XM(3) (-) and X(2)M(3) metallic clusters. Our results also show that the aromaticity of the cyclo-[M(3)](2-) unit in the X(2)M(3) metallic clusters depends on the nature of X and M. Moreover, we explored the possibility for tuning the aromaticity by simply moving X perpendicularly to the center of the M(3) ring. The Na(2)Mg(3), Li(2)Mg(3), and X(2)Ca(3) clusters undergo drastic aromaticity alterations when changing the distance from X to the center of the M(3) ring, whereas X(2)Be(3) and K(2)Mg(3) keep its aromaticity relatively constant along this process. (c) 2009 Wiley Periodicals, Inc.

  8. Growth of cluster assembled ZnO film by nanocluster beam deposition technique

    SciTech Connect

    Halder, Nilanjan

    2015-06-24

    ZnO is considered as one of the most promising material for optoelectronic devices. The present work emphasizes production of cluster assembled ZnO films by a UHV nanocluster beam deposition technique where the nanoclusters were produced in a laser vaporization cluster source. The microstructural and the optical properties of the ZnO nanocluster film deposited were investigated. As the wet chemical processes are not compatible with current solid state methods of device fabrication, therefore alternative UHV technique described in the paper is the need of the hour.

  9. Fundamental Studies of Underpotential Metal Deposition and Trace Analysis Using Solid Electrodes.

    DTIC Science & Technology

    1982-01-01

    7AD-At30 099 FUNDAMENTAL STUDIES OF UNDERPOTENTIAL METAL DEPOSITION 1 BUFFALO DEPT OF CHEMISTRY S BRUCKENSTEIN 1982 UNCLASSIFIED AFOSR-TR-83-0557...T’S CAT A--CG t,-V5EP A . ITE(ad utilS TYPE OF REPCRT 0 0 .’EOEt’ Fundamental Studies of Underpotential Metal Final Deposition and Trace411111110...siectrocatalyls (by underpotential metal deposition ). A second objective was to develop new approaches to studying electrcxhemical reactions at solid

  10. Towards production of novel catalyst powders from supported size-selected clusters by multilayer deposition and dicing

    NASA Astrophysics Data System (ADS)

    Jian, Nan; Bauer, Karl; Palmer, Richard E.

    2017-08-01

    A multilayer deposition method has been developed with the potential to capture and process atomic clusters generated by a high flux cluster beam source. In this deposition mode a series of sandwich structures each consisting of three layers—a carbon support layer, cluster layer and polymer release layer—is sequentially deposited to form a stack of isolated cluster layers, as confirmed by through-focal aberration-corrected HAADF STEM analysis. The stack can then be diced into small pieces by a mechanical saw. The diced pieces are immersed in solvent to dissolve the polymer release layer and form small platelets of supported clusters.

  11. Towards production of novel catalyst powders from supported size-selected clusters by multilayer deposition and dicing.

    PubMed

    Jian, Nan; Bauer, Karl; Palmer, Richard E

    2017-08-11

    A multilayer deposition method has been developed with the potential to capture and process atomic clusters generated by a high flux cluster beam source. In this deposition mode a series of sandwich structures each consisting of three layers-a carbon support layer, cluster layer and polymer release layer-is sequentially deposited to form a stack of isolated cluster layers, as confirmed by through-focal aberration-corrected HAADF STEM analysis. The stack can then be diced into small pieces by a mechanical saw. The diced pieces are immersed in solvent to dissolve the polymer release layer and form small platelets of supported clusters.

  12. Size control of noble metal clusters and metallic heterostructures through the reduction kinetics of metal precursors

    NASA Astrophysics Data System (ADS)

    Sevonkaev, Igor V.; Herein, Daniel; Jeske, Gerald; Goia, Dan V.

    2014-07-01

    Eight precious metal salts/complexes were reduced in propylene glycol at temperatures ranging between 110 and 170 °C. We found that the reduction temperature and the size of precipitated metallic nanoparticles formed were significantly affected by the structure and reactivity of the metal precursors. The choice of noble metal precursor offers flexibility for designing, fabricating and controlling the size of metallic heterostructures with tunable properties.Eight precious metal salts/complexes were reduced in propylene glycol at temperatures ranging between 110 and 170 °C. We found that the reduction temperature and the size of precipitated metallic nanoparticles formed were significantly affected by the structure and reactivity of the metal precursors. The choice of noble metal precursor offers flexibility for designing, fabricating and controlling the size of metallic heterostructures with tunable properties. Electronic supplementary information (ESI) available. See DOI: 10.1039/c4nr03045a

  13. Atmospherically deposited trace metals from bulk mineral concentrate port operations.

    PubMed

    Taylor, Mark Patrick

    2015-05-15

    Although metal exposures in the environment have declined over the last two decades, certain activities and locations still present a risk of harm to human health. This study examines environmental dust metal and metalloid hazards (arsenic, cadmium, lead and nickel) associated with bulk mineral transport, loading and unloading port operations in public locations and children's playgrounds in the inner city of Townsville, northern Queensland. The mean increase in lead on post-play hand wipes (965 μg/m(2)/day) across all sites was more than 10-times the mean pre-play loadings (95 μg/m(2)/day). Maximum loading values after a 10-minute play period were 3012 μg/m(2), more than seven times the goal of 400 μg/m(2) used by the Government of Western Australia (2011). Maximum daily nickel post-play hand loadings (404 μg/m(2)) were more than 26 times above the German Federal Immission Control Act 2002 annual benchmark of 15 μg/m(2)/day. Repeat sampling over the 5-day study period showed that hands and surfaces were re-contaminated daily from the deposition of metal-rich atmospheric dusts. Lead isotopic composition analysis of dust wipes ((208)Pb/(207)Pb and (206)Pb/(207)Pb) showed that surface dust lead was similar to Mount Isa type ores, which are exported through the Port of Townsville. While dust metal contaminant loadings are lower than other mining and smelting towns in Australia, they exceeded national and international benchmarks for environmental quality. The lessons from this study are clear - even where operations are considered acceptable by managing authorities, targeted assessment and monitoring can be used to evaluate whether current management practices are truly best practice. Reassessment can identify opportunities for improvement and maximum environmental and human health protection. Copyright © 2015 Elsevier B.V. All rights reserved.

  14. Antiferromagnetic resonance in alkali-metal clusters in sodalite

    NASA Astrophysics Data System (ADS)

    Nakano, Takehito; Tsugeno, Hajime; Hanazawa, Atsufumi; Kashiwagi, Takanari; Nozue, Yasuo; Hagiwara, Masayuki

    2013-11-01

    We have performed electron spin resonance (ESR) studies of K43+ and (K3Rb)3+ nanoclusters incorporated in powder specimens of aluminosilicate sodalite at several microwave frequencies between 9 and 34 GHz. The K43+ and (K3Rb)3+ clusters are arrayed in a bcc structure and are known to show antiferromagnetic ordering below the Néel temperatures of TN ≃72 and ≃80 K, respectively, due to the exchange coupling between s electrons confined in the clusters. We have found sudden broadenings of ESR spectra in both samples below TN. The line shape of the spectra below TN is analyzed by powder pattern simulations of antiferromagnetic resonance (AFMR) spectra. The calculated line shapes well reproduce the experimental ones at all the frequencies by assuming a biaxial magnetic anisotropy. We have evaluated extremely small anisotropy fields of approximately 1 Oe indicating that these materials are ideal Heisenberg antiferromagnets. We have also found that the magnetic anisotropy changes from easy-plane type to uniaxial type by changing into a heavier alkali-metal cluster and that the g value shifts to a large value beyond two below TN for K43+ and (K3Rb)3+ nanoclusters. These novel features of K43+ and (K3Rb)3+ nanoclusters incorporated in sodalite are discussed.

  15. Model catalysis by size-selected cluster deposition

    SciTech Connect

    Anderson, Scott

    2015-11-20

    This report summarizes the accomplishments during the last four years of the subject grant. Results are presented for experiments in which size-selected model catalysts were studied under surface science and aqueous electrochemical conditions. Strong effects of cluster size were found, and by correlating the size effects with size-dependent physical properties of the samples measured by surface science methods, it was possible to deduce mechanistic insights, such as the factors that control the rate-limiting step in the reactions. Results are presented for CO oxidation, CO binding energetics and geometries, and electronic effects under surface science conditions, and for the electrochemical oxygen reduction reaction, ethanol oxidation reaction, and for oxidation of carbon by water.

  16. The Growth Mechanism of Transition Metal Dichalcogenides by using Sulfurization of Pre-deposited Transition Metals and the 2D Crystal Hetero-structure Establishment

    PubMed Central

    Wu, Chong-Rong; Chang, Xiang-Rui; Wu, Chao-Hsin; Lin, Shih-Yen

    2017-01-01

    A growth model is proposed for the large-area and uniform MoS2 film grown by using sulfurization of pre-deposited Mo films on sapphire substrates. During the sulfurization procedure, the competition between the two mechanisms of the Mo oxide segregation to form small clusters and the sulfurization reaction to form planar MoS2 film is determined by the amount of background sulfur. Small Mo oxide clusters are observed under the sulfur deficient condition, while large-area and complete MoS2 films are obtained under the sulfur sufficient condition. Precise layer number controllability is also achieved by controlling the pre-deposited Mo film thicknesses. The drain currents in positive dependence on the layer numbers of the MoS2 transistors with 1-, 3- and 5- layer MoS2 have demonstrated small variation in material characteristics between each MoS2 layer prepared by using this growth technique. By sequential transition metal deposition and sulfurization procedures, a WS2/MoS2/WS2 double hetero-structure is demonstrated. Large-area growth, layer number controllability and the possibility of hetero-structure establishment by using sequential metal deposition and following sulfurization procedures have revealed the potential of this growth technique for practical applications. PMID:28176836

  17. The Growth Mechanism of Transition Metal Dichalcogenides by using Sulfurization of Pre-deposited Transition Metals and the 2D Crystal Hetero-structure Establishment

    NASA Astrophysics Data System (ADS)

    Wu, Chong-Rong; Chang, Xiang-Rui; Wu, Chao-Hsin; Lin, Shih-Yen

    2017-02-01

    A growth model is proposed for the large-area and uniform MoS2 film grown by using sulfurization of pre-deposited Mo films on sapphire substrates. During the sulfurization procedure, the competition between the two mechanisms of the Mo oxide segregation to form small clusters and the sulfurization reaction to form planar MoS2 film is determined by the amount of background sulfur. Small Mo oxide clusters are observed under the sulfur deficient condition, while large-area and complete MoS2 films are obtained under the sulfur sufficient condition. Precise layer number controllability is also achieved by controlling the pre-deposited Mo film thicknesses. The drain currents in positive dependence on the layer numbers of the MoS2 transistors with 1-, 3- and 5- layer MoS2 have demonstrated small variation in material characteristics between each MoS2 layer prepared by using this growth technique. By sequential transition metal deposition and sulfurization procedures, a WS2/MoS2/WS2 double hetero-structure is demonstrated. Large-area growth, layer number controllability and the possibility of hetero-structure establishment by using sequential metal deposition and following sulfurization procedures have revealed the potential of this growth technique for practical applications.

  18. Chemical vapour deposition: Transition metal carbides go 2D

    DOE PAGES

    Gogotsi, Yury

    2015-08-17

    Here, the research community has been steadily expanding the family of few-atom-thick crystals beyond graphene, discovering new materials or producing known materials in a 2D state and demonstrating their unique properties1, 2. Recently, nanometre-thin 2D transition metal carbides have also joined this family3. Writing in Nature Materials, Chuan Xu and colleagues now report a significant advance in the field, showing the synthesis of large-area, high-quality, nanometre-thin crystals of molybdenum carbide that demonstrate low-temperature 2D superconductivity4. Moreover, they also show that other ultrathin carbide crystals, such as tungsten and tantalum carbides, can be grown by chemical vapour deposition with a highmore » crystallinity and very low defect concentration.« less

  19. Self-pumping impurity by in-situ metal deposition

    SciTech Connect

    Brooks, J.N.; Mattas, R.F.

    1983-07-01

    A system for in-situ removal of helium trapping in freshly deposited metal surface layers of a limiter or divertor has been studied. The system would trap helium on a limiter front surface, or a divertor plate, at low plasma edge temperatures, or in a limiter slot region, at high edge temperatures. Fresh material, introduced to the plasma and/or scrape-off zone, would be added at a rate of about five times the alpha production rate. The material would be reprocessed periodically, e.g. once a year. Possible materials are nickel, vanadium, niobium, and tantalum. Advantages of a self-pumping system are the absence of vacuum ducts and pumps, and the minimization of tritium processing and inventory.

  20. Laser Metal Deposition of the Intermetallic TiAl Alloy

    NASA Astrophysics Data System (ADS)

    Thomas, Marc; Malot, Thierry; Aubry, Pascal

    2017-03-01

    Laser metal deposition of the commercial intermetallic Ti-47Al-2Cr-2Nb alloy was investigated. A large number of experiments were conducted under controlled atmosphere by changing the processing parameters to manufacture a series of beads, thin walls, and massive blocks. Optimal process parameters were successfully found to prevent cracking which is generally observed in this brittle material due to built-up residual stresses during fast cooling. These non-equilibrium cooling conditions tend to generate ultra-fine and metastable structures exhibiting high microhardness values, thus requiring post-heat treatments. The latter were successfully used to restore homogeneous lamellar or duplex microstructures and to relieve residual stresses. Subsequent tensile tests enabled us to validate the soundness and homogeneity of the Intermetallic TiAl alloy. Finally, a higher mechanical performance was achieved for the LMD material with respect to cast+HIP and EBM counterparts.

  1. Laser Metal Deposition of the Intermetallic TiAl Alloy

    NASA Astrophysics Data System (ADS)

    Thomas, Marc; Malot, Thierry; Aubry, Pascal

    2017-06-01

    Laser metal deposition of the commercial intermetallic Ti-47Al-2Cr-2Nb alloy was investigated. A large number of experiments were conducted under controlled atmosphere by changing the processing parameters to manufacture a series of beads, thin walls, and massive blocks. Optimal process parameters were successfully found to prevent cracking which is generally observed in this brittle material due to built-up residual stresses during fast cooling. These non-equilibrium cooling conditions tend to generate ultra-fine and metastable structures exhibiting high microhardness values, thus requiring post-heat treatments. The latter were successfully used to restore homogeneous lamellar or duplex microstructures and to relieve residual stresses. Subsequent tensile tests enabled us to validate the soundness and homogeneity of the Intermetallic TiAl alloy. Finally, a higher mechanical performance was achieved for the LMD material with respect to cast+HIP and EBM counterparts.

  2. Chemical vapour deposition: Transition metal carbides go 2D

    SciTech Connect

    Gogotsi, Yury

    2015-08-17

    Here, the research community has been steadily expanding the family of few-atom-thick crystals beyond graphene, discovering new materials or producing known materials in a 2D state and demonstrating their unique properties1, 2. Recently, nanometre-thin 2D transition metal carbides have also joined this family3. Writing in Nature Materials, Chuan Xu and colleagues now report a significant advance in the field, showing the synthesis of large-area, high-quality, nanometre-thin crystals of molybdenum carbide that demonstrate low-temperature 2D superconductivity4. Moreover, they also show that other ultrathin carbide crystals, such as tungsten and tantalum carbides, can be grown by chemical vapour deposition with a high crystallinity and very low defect concentration.

  3. Pulsed laser deposition of transition metal oxides for secondary batteries

    SciTech Connect

    Striebel, K.A.; Deng, C.Z.; Cairns, E.J.

    1995-12-31

    Pulsed laser deposition has been used to prepare thin films of several complex metal oxides of significance in secondary batteries from a single stoichiometric target with a substrate temperature of 600 C in the presence of 200 mtorr O{sub 2}. Films of the candidate bifunctional air electrocatalysts, for metal air batteries, La{sub 0.6}Ca{sub 0.4}CoO{sub 3}, La{sub 0.6}Sr{sub 0.4}CoO{sub 3}, La{sub 0.6}Ca{sub 0.4}MnO{sub 3} and La{sub 0.6}Sr{sub 0.4}MnO{sub 3} were prepared on glassy carbon substrates. Glassy carbon was found to either erode during the ablation process (with the cobaltates) or cause film cracking after deposition because of its extremely low coefficient of thermal expansion. The use of stainless steel substrates yielded 0.3 {micro}m-thick dense films of La{sub 0.6}Ca{sub 0.4}CoO{sub 3} and La{sub 0.6}Ca{sub 0.4}MnO{sub 3} which were suitable for electrochemical measurements in concentrated alkaline electrolytes. LiMn{sub 2}O{sub 4} and LiCoO{sub 2} films were prepared at thickness` of 0.3 {micro}m and 1.5 {micro}m. The 0.3 {micro}m-thick films delivered 176 mC/cm{sup 2}-{micro}m and 323 mC/cm{sup 2} for LiMn{sub 2}O{sub 4} and LiCoO{sub 2}, respectively, in 1 M LiClO{sub 4}/PC.

  4. Sulphur in the metal poor globular cluster NGC 6397

    NASA Astrophysics Data System (ADS)

    Koch, A.; Caffau, E.

    2011-10-01

    Sulphur (S) is a non-refractory α-element that is not locked into dust grains in the interstellar medium. Thus no correction to the measured, interstellar sulphur abundance is needed and it can be readily compared to the S content in stellar photospheres. Here we present the first measurement of sulphur in the metal poor globular cluster (GC) NGC 6397, as detected in a MIKE/Magellan high signal-to-noise, high-resolution spectrum of one red giant star. While abundance ratios of sulphur are available for a larger number of Galactic stars down to an [Fe/H] of ~ -3.5 dex, no measurements in globular clusters more metal poor than -1.5 dex have been reported so far. We find aNLTE, 3-D abundance ratio of [S/Fe] = +0.52 ± 0.20 (stat.) ± 0.08 (sys.), based on theS I, Multiplet 1 line at 9212.8 Å. This value is consistent with a Galactic halo plateau as typical of other α-elements in GCs and field stars, but we cannot rule out its membership with a second branch of increasing [S/Fe] with decreasing [Fe/H], claimed in the literature, which leads to a large scatter at metallicities around - 2 dex. The [S/Mg] and [S/Ca] ratios in this star are compatible with a Solar value to within the (large) uncertainties. Despite the very large scatter in these ratios across Galactic stars between literature samples, this indicates that sulphur traces the chemical imprints of the other α-elements in metal poor GCs. Combined with its moderate sodium abundance ([S/Na]NLTE = 0.48), the [S/Fe] ratio in this GC extends a global, positive S-Na correlation that is not seen in field stars and might indicate that proton-capture reactions contributed to the production of sulphur in the (metal poor) early GC environments. This paper includes data gathered with the 6.5 m Magellan Telescopes located at Las Campanas Observatory, Chile.

  5. Interfacial bond strength of electrophoretically deposited hydroxyapatite coatings on metals.

    PubMed

    Wei, M; Ruys, A J; Swain, M V; Kim, S H; Milthorpe, B K; Sorrell, C C

    1999-07-01

    Hydroxyapatite (HAp) coatings were deposited onto substrates of metal biomaterials (Ti, Ti6Al4V, and 316L stainless steel) by electrophoretic deposition (EPD). Only ultra-high surface area HAp powder, prepared by the metathesis method 10Ca(NO3)2 + 6(NH4)2HPO4 + 8NH4OH), could produce dense coatings when sintered at 875-1000degreesC. Single EPD coatings cracked during sintering owing to the 15-18% sintering shrinkage, but the HAp did not decompose. The use of dual coatings (coat, sinter, coat, sinter) resolved the cracking problem. Scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) inspection revealed that the second coating filled in the "valleys" in the cracks of the first coating. The interfacial shear strength of the dual coatings was found, by ASTM F1044-87, to be approximately 12 MPa on a titanium substrate and approximately 22 MPa on 316L stainless steel, comparing quite favorably with the 34 MPa benchmark (the shear strength of bovine cortical bone was found to be 34 MPa). Stainless steel gave the better result since -316L (20.5 microm mK(-1)) > alpha-HAp (approximately 14 microm mK(-1)), resulting in residual compressive stresses in the coating, whereas alpha-titanium (approximately 10.3 microm mK(-1)) < alpha-HAp, resulting in residual tensile stresses in the coating.

  6. Controlled Mechanical Cracking of Metal Films Deposited on Polydimethylsiloxane (PDMS)

    PubMed Central

    Polywka, Andreas; Stegers, Luca; Krauledat, Oliver; Riedl, Thomas; Jakob, Timo; Görrn, Patrick

    2016-01-01

    Stretchable large area electronics conform to arbitrarily-shaped 3D surfaces and enables comfortable contact to the human skin and other biological tissue. There are approaches allowing for large area thin films to be stretched by tens of percent without cracking. The approach presented here does not prevent cracking, rather it aims to precisely control the crack positions and their orientation. For this purpose, the polydimethylsiloxane (PDMS) is hardened by exposure to ultraviolet radiation (172 nm) through an exposure mask. Only well-defined patterns are kept untreated. With these soft islands cracks at the hardened surface can be controlled in terms of starting position, direction and end position. This approach is first investigated at the hardened PDMS surface itself. It is then applied to conductive silver films deposited from the liquid phase. It is found that statistical (uncontrolled) cracking of the silver films can be avoided at strain below 35%. This enables metal interconnects to be integrated into stretchable networks. The combination of controlled cracks with wrinkling enables interconnects that are stretchable in arbitrary and changing directions. The deposition and patterning does not involve vacuum processing, photolithography, or solvents.

  7. Probing the History of Galaxy Clusters with Metallicity and Entropy Measurements

    NASA Astrophysics Data System (ADS)

    Elkholy, Tamer Yohanna

    Galaxy clusters are the largest gravitationally bound objects found today in our Universe. The gas they contain, the intra-cluster medium (ICM), is heated to temperatures in the approximate range of 1 to 10 keV, and thus emits X-ray radiation. Studying the ICM through the spatial and spectral analysis of its emission returns the richest information about both the overall cosmological context which governs the formation of clusters, as well as the physical processes occurring within. The aim of this thesis is to learn about the history of the physical processes that drive the evolution of galaxy clusters, through careful, spatially resolved measurements of their metallicity and entropy content. A sample of 45 nearby clusters observed with Chandra is analyzed to produce radial density, temperature, entropy and metallicity profiles. The entropy profiles are computed to larger radial extents than in previous Chandra analyses. The results of this analysis are made available to the scientific community in an electronic database. Comparing metallicity and entropy in the outskirts of clusters, we find no signature on the entropy profiles of the ensemble of supernovae that produced the observed metals. In the centers of clusters, we find that the metallicities of high-mass clusters are much less dispersed than those of low-mass clusters. A comparison of metallicity with the regularity of the X-ray emission morphology suggests that metallicities in low-mass clusters are more susceptible to increase from violent events such as mergers. We also find that the variation in the stellar-to-gas mass ratio as a function of cluster mass can explain the variation of central metallicity with cluster mass, only if we assume that there is a constant level of metallicity for clusters of all masses, above which the observed galaxies add more metals in proportion to their mass. (Copies available exclusively from MIT Libraries, libraries.mit.edu/docs - docs mit.edu)

  8. Method of depositing buffer layers on biaxially textured metal substrates

    DOEpatents

    Beach, David B.; Morrell, Jonathan S.; Paranthaman, Mariappan; Chirayil, Thomas; Specht, Eliot D.; Goyal, Amit

    2002-08-27

    A laminate article comprises a substrate and a biaxially textured (RE.sup.1.sub.x RE.sup.2.sub.(1-x)).sub.2 O.sub.3 buffer layer over the substrate, wherein 0deposited using sol-gel or metal-organic decomposition. The laminate article can include a layer of YBCO over the (RE.sup.1.sub.x RE.sup.2.sub.(1-x)).sub.2 O.sub.3 buffer layer. A layer of CeO.sub.2 between the YBCO layer and the (RE.sup.1.sub.x RE.sup.2.sub.(1-x)).sub.2 O.sub.3 buffer can also be include. Further included can be a layer of YSZ between the CeO.sub.2 layer and the (RE.sup.1.sub.x RE.sup.2.sub.(1-x)).sub.2 O.sub.3 buffer layer. The substrate can be a biaxially textured metal, such as nickel. A method of forming the laminate article is also disclosed.

  9. Shape deposition manufacturing of smart metallic structures with embedded sensors

    NASA Astrophysics Data System (ADS)

    Li, Xiaochun; Golnas, Anastasios; Prinz, Fritz B.

    2000-06-01

    The need to obtain information on the performance and lifetime of a tool in service is of prime importance to many industries. It calls for on-line acquisition of information such as temperature and strain values from tools and structures. With embedded sensors, structures are capable of monitoring parameters at critical locations not accessible to ordinary sensors. To embed sensors in the functional structures, especially structures, Shape Deposition Manufacturing (SDM) is a methodology capable of integrating sensors during the production of tooling or structural components. Thin film sensors and fiber optic sensors have been identified as two promising candidates to be integrated in metallic structures. Embedded thin film strain gages have been characterized in a four-point bending test and the results, showing linearity and no hysteresis, match with those from the theoretical model and commercially available strain gages. Fiber optic sensors have been successfully embedded in nickel and stainless steel structures. The embedded fiber optic sensors have been used to measure temperatures and strains. They provide higher sensitivity, good accuracy, and high temperature capacity. Based on fiber optic sensor embedding techniques, a remote temperature/strain sensing system suitable rotating objects, such as turbine blades, has been developed. The developed techniques can be harnessed for rapid prototyping of smart metallic structures.

  10. Multipronged mapping to the dynamics of a barium atom deposited on argon clusters.

    PubMed

    Awali, S; Gaveau, M-A; Briant, M; Mestdagh, J-M; Soep, B; Gobert, O; Maksimenka, R; Poisson, L

    2016-11-30

    The dynamics of an electronically excited barium atom deposited at the surface of an Ar≈500 cluster was explored in a multipronged approach which associates information from frequency-resolved nanosecond experiments and information from femtosecond time-resolved experiments. In both types of experiments, the dynamics is monitored by photoelectron and photoion spectroscopy.

  11. Controllable Deposition of Alloy Clusters or Nanoparticles Catalysts on Carbon Surfaces

    SciTech Connect

    Sasaki, K.; Ando, Y.; Su, D.; Adzic, R.

    2011-08-15

    We describe a simple method for controllably depositing Pt-Ru alloy nanoparticles on carbon surfaces that is mediated by Pb or Cu adlayers undergoing underpotential deposition and stripping during Pt and Ru codeposition at diffusion-limiting currents. The amount of surface Pt atoms deposited largely reflects the number of potential cycles causing the deposition and stripping of the metal adlayer at underpotentials, the metal species used as a mediator, and the scan rate of the potential cycles. We employed electrochemical methanol oxidation to gain information on the catalyst's activities. The catalysts with large amounts of surface Pt atoms have relatively high methanol-oxidation activity. Catalysts prepared using this method enhance methanol-oxidation activity per electrode surface area, while maintaining catalytic activity per surface Pt atom; thus, the amount of Pt is reduced in comparison with conventional methanol-oxidation catalysts. The method is suitable for efficient synthesizing various bimetallic catalysts.

  12. All-metal clusters that mimic the chemistry of halogens.

    PubMed

    Zhao, Tianshan; Li, Yawei; Wang, Qian; Jena, Puru

    2013-10-07

    Owing to their s(2)p(5) electronic configuration, halogen atoms are highly electronegative and constitute the anionic components of salts. Whereas clusters that contain no halogen atoms, such as AlH(4), mimic the chemistry of halogens and readily form salts (e.g., Na(+)(AlH(4))(-)), clusters that are solely composed of metal atoms and yet behave in the same manner as a halogen are rare. Because coinage-metal atoms (Cu, Ag, and Au) only have one valence electron in their outermost electronic shell, as in H, we examined the possibility that, on interacting with Al, in particular as AlX(4) (X=Cu, Ag, Au), these metal atoms may exhibit halogen-like properties. By using density functional theory, we show that AlAu(4) not only mimics the chemistry of halogens, but also, with a vertical detachment energy (VDE) of 3.98 eV in its anionic form, is a superhalogen. Similarly, analogous to XHX superhalogens (X=F, Cl, Br), XAuX species with VDEs of 4.65, 4.50, and 4.34 eV in their anionic form, respectively, also form superhalogens. In addition, Au can also form hyperhalogens, a recently discovered species that show electron affinities (EAs) that are even higher than those of their corresponding superhalogen building blocks. For example, the VDEs of M(AlAu(4))(2)(-) (M=Na and K) and anionic (FAuF)Au(FAuF) range from 4.06 to 5.70 eV. Au-based superhalogen anions, such as AlAu(4)(-) and AuF(2)(-), have the additional advantage that they exhibit wider optical absorption ranges than their H-based analogues, AlH(4)(-) and HF(2)(-). Because of the catalytic properties and the biocompatibility of Au, Au-based superhalogens may be multifunctional. However, similar studies that were carried out for Cu and Ag atoms have shown that, unlike AlAu(4), AlX(4) (X=Cu, Ag) clusters are not superhalogens, a property that can be attributed to the large EA of the Au atom.

  13. Study of globular cluster M53: new variables, distance, metallicity

    NASA Astrophysics Data System (ADS)

    Dékány, I.; Kovács, G.

    2009-11-01

    Aims: We study the variable star content of the globular cluster M53 to compute the physical parameters of the constituting stars and the distance of the cluster. Methods: Covering two adjacent seasons in 2007 and 2008, new photometric data are gathered for 3048 objects in the field of M53. By using the OIS (optimal image subtraction) method and subsequently TFA (trend filtering algorithm), we search for variables in the full sample by using discrete Fourier transformation and box-fitting least squares methods. We select variables based on the statistics related to these methods combined with visual inspection. Results: We identified 12 new variables (2 RR Lyrae stars, 7 short periodic stars - 3 of them are SX Phe stars - and 3 long-period variables). No eclipsing binaries were found in the present sample. Except for the 3 (hitherto unknown) Blazhko RR Lyrae (two RRab and an RRc) stars, no multiperiodic variables were found. We showed that after proper period shift, the PLC (period-luminosity-color) relation for the first overtone RR Lyrae sample tightly follows the one spanned by the fundamental stars. Furthermore, the slope is in agreement with that derived from other clusters. Based on the earlier Baade-Wesselink calibration of the PLC relations, the derived reddening-free distance modulus of M53 is 16.31±0.04 mag, corresponding to a distance modulus of 18.5 mag for the Large Magellanic Cloud. From the Fourier parameters of the RRab stars we obtained an average iron abundance of -1.58± 0.03 (error of the mean). This is ~0.5 dex higher than the overall abundance of the giants as given in the literature and derived in this paper from the three-color photometry of giants. We suspect that the source of this discrepancy (observable also in other, low-metallicity clusters) is the lack of a sufficient number of low-metallicity objects in the calibrating sample of the Fourier method. Table 1 is only available in electronic form at http://www.aanda.org Photometric data

  14. Magnetically controlled deposition of metals using gas plasma. Final report

    SciTech Connect

    1998-04-02

    This is the first phase of a project that has the objective to develop a method of spraying materials on a substrate in a controlled manner to eliminate the waste and hazardous material generation inherent in present plating processes. The project is considering plasma spraying of metal on a substrate using magneto-hydrodynamics to control the plasma/metal stream. The process being developed is considering the use of commercially available plasma torches to generate the plasma/metal stream. The plasma stream is collimated, and directed using magnetic forces to the extent required for precise control of the deposition material. The project will be completed in phases. Phase one of the project, the subject of this grant, is the development of an analytical model that can be used to determine the feasibility of the process and to design a laboratory scale demonstration unit. The contracted time is complete, and the research is still continuing. This report provides the results obtained to date. As the model and calculations are completed those results will also be provided. This report contains the results of the computer code that have been completed to date. Results from a ASMEE Benchmark problem, flow over a backward step with heat transfer, Couette flow with magnetic forces, free jet flow are presented along with several other check calculations that are representative of the cases that were calculated in the course of the development process. The final cases that define a velocity field in the exit of a plasma spray torch with and without a magnetic field are in process. A separate program (SPRAY) has been developed that can track the plating material to the substrate and describe the distribution of the material on the substrate. When the jet calculations are complete SPRAY will be used to compare the distribution of material on the substrate with and without the effect of the magnetic focus.

  15. High-dispersion spectroscopy of giants in metal-poor globular clusters. I - Iron abundances

    NASA Technical Reports Server (NTRS)

    Minniti, Dante; Geisler, Doug; Peterson, Ruth C.; Claria, Juan J.

    1993-01-01

    High-resolution, high-SNR CCD spectra have been obtained for 16 giants in eight metal-poor Galactic globular clusters. Fe abundances accurate to 0.15 dex have been determined by a fully consistent set of model atmospheres and spectrum synthesis techniques. A metallicity scale is presented for metal-poor clusters that should prove useful for calibrating a wide variety of photometric and low-resolution spectroscopic metallicity indicators.

  16. High-dispersion spectroscopy of giants in metal-poor globular clusters. I - Iron abundances

    NASA Technical Reports Server (NTRS)

    Minniti, Dante; Geisler, Doug; Peterson, Ruth C.; Claria, Juan J.

    1993-01-01

    High-resolution, high-SNR CCD spectra have been obtained for 16 giants in eight metal-poor Galactic globular clusters. Fe abundances accurate to 0.15 dex have been determined by a fully consistent set of model atmospheres and spectrum synthesis techniques. A metallicity scale is presented for metal-poor clusters that should prove useful for calibrating a wide variety of photometric and low-resolution spectroscopic metallicity indicators.

  17. A difference in using atomic layer deposition or physical vapour deposition TiN as electrode material in metal-insulator-metal and metal-insulator-silicon capacitors.

    PubMed

    Groenland, A W; Wolters, R A M; Kovalgin, A Y; Schmitz, J

    2011-09-01

    In this work, metal-insulator-metal (MIM) and metal-insulator-silicon (MIS) capacitors are studied using titanium nitride (TiN) as the electrode material. The effect of structural defects on the electrical properties on MIS and MIM capacitors is studied for various electrode configurations. In the MIM capacitors the bottom electrode is a patterned 100 nm TiN layer (called BE type 1), deposited via sputtering, while MIS capacitors have a flat bottom electrode (called BE type 2-silicon substrate). A high quality 50-100 nm thick SiO2 layer, made by inductively-coupled plasma CVD at 150 degrees C, is deposited as a dielectric on top of both types of bottom electrodes. BE type 1 (MIM) capacitors have a varying from low to high concentration of structural defects in the SiO2 layer. BE type 2 (MIS) capacitors have a low concentration of structural defects and are used as a reference. Two sets of each capacitor design are fabricated with the TiN top electrode deposited either via physical vapour deposition (PVD, i.e., sputtering) or atomic layer deposition (ALD). The MIM and MIS capacitors are electrically characterized in terms of the leakage current at an electric field of 0.1 MV/cm (I leak) and for different structural defect concentrations. It is shown that the structural defects only show up in the electrical characteristics of BE type 1 capacitors with an ALD TiN-based top electrode. This is due to the excellent step coverage of the ALD process. This work clearly demonstrates the sensitivity to process-induced structural defects, when ALD is used as a step in process integration of conductors on insulation materials.

  18. A DFT study of volatile organic compounds adsorption on transition metal deposited graphene

    NASA Astrophysics Data System (ADS)

    Kunaseth, Manaschai; Poldorn, Preeyaporn; Junkeaw, Anchalee; Meeprasert, Jittima; Rungnim, Chompoonut; Namuangruk, Supawadee; Kungwan, Nawee; Inntam, Chan; Jungsuttiwong, Siriporn

    2017-02-01

    Recently, elevated global emission of volatile organic compounds (VOCs) was associated to the acceleration and increasing severity of climate change worldwide. In this work, we investigated the performance of VOCs removal via modified carbon-based adsorbent using density functional theory. Here, four transition metals (TMs) including Pd, Pt, Ag, and Au were deposited onto single-vacancy defective graphene (SDG) surface to increase the adsorption efficiency. Five prototypical VOCs including benzene, furan, pyrrole, pyridine, and thiophene were used to study the adsorption capability of metal-deposited graphene adsorbent. Calculation results revealed that Pd, Pt, Au, and Ag atoms and nanoclusters bind strongly onto the SDG surface. In this study, benzene, furan and pyrrole bind in the π-interaction mode using delocalized π-electron in aromatic ring, while pyridine and thiophene favor X- interaction mode, donating lone pair electron from heteroatom. In terms of adsorption, pyridine VOC adsorption strengths to the TM-cluster doped SDG surfaces are Pt4 (-2.11 eV) > Pd4 (-2.05 eV) > Ag4 (-1.53 eV) > Au4 (-1.87 eV). Our findings indicate that TM-doped SDG is a suitable adsorbent material for VOC removal. In addition, partial density of states analysis suggests that benzene, furan, and pyrrole interactions with TM cluster are based on p-orbitals of carbon atoms, while pyridine and thiophene interactions are facilitated by hybridized sp2-orbitals of heteroatoms. This work provides a key insight into the fundamentals of VOCs adsorption on carbon-based adsorbent.

  19. Monitoring the dissolution process of metals in the gas phase: reactions of nanoscale Al and Ga metal atom clusters and their relationship to similar metalloid clusters.

    PubMed

    Burgert, Ralf; Schnöckel, Hansgeorg

    2008-05-14

    Formation and dissolution of metals are two of the oldest technical chemical processes. On the atomic scale, these processes are based on the formation and cleavage of metal-metal bonds. During the past 15 years we have studied intensively the intermediates during the formation process of metals, i.e. the formation of compounds containing many metal-metal bonds between naked metal atoms in the center and ligand-bearing metal atoms at the surface. We have called the clusters metalloid or, more generally, elementoid clusters. Via a retrosynthetic route, the many different Al and Ga metalloid clusters which have been structurally characterized allow us to understand also the dissolution process; i.e. the cleavage of metal-metal (M-M) bonds. However, this process can be detected much more directly by the reaction of single metal atom clusters in the gas phase under high vacuum conditions. A suitable tool to monitor the dissolution process of a metal cluster in the gas phase is FT-ICR (Fourier transform ion cyclotron resonance) mass spectrometry. Snapshots during these cleavage processes are possible because only every 1-10 s is there a contact between a cluster molecule and an oxidizing molecule (e.g. Cl2). This period is long, i.e. the formation of the primary product (a smaller metal atom cluster) is finished before the next collision happens. We have studied three different types of reaction:(1) Step-by-step fragmentation of a structurally known metalloid cluster allows us to understand the bonding principle of these clusters because in every step only the weakest bond is broken.(2) There are three oxidation reactions of an Al13(-) cluster molecule with Cl2, HCl and O2 central to this review. These three reactions represent three different reaction types, (a) an exothermic reaction (Cl2), (b) an endothermic reaction (HCl), and (c) a kinetically limited reaction based on spin conservation rules (O2).(3) Finally, we present the reaction of a metalloid cluster with Cl2

  20. Atomically precise arrays of fluorescent silver clusters: a modular approach for metal cluster photonics on DNA nanostructures.

    PubMed

    Copp, Stacy M; Schultz, Danielle E; Swasey, Steven; Gwinn, Elisabeth G

    2015-03-24

    The remarkable precision that DNA scaffolds provide for arraying nanoscale optical elements enables optical phenomena that arise from interactions of metal nanoparticles, dye molecules, and quantum dots placed at nanoscale separations. However, control of ensemble optical properties has been limited by the difficulty of achieving uniform particle sizes and shapes. Ligand-stabilized metal clusters offer a route to atomically precise arrays that combine desirable attributes of both metals and molecules. Exploiting the unique advantages of the cluster regime requires techniques to realize controlled nanoscale placement of select cluster structures. Here we show that atomically monodisperse arrays of fluorescent, DNA-stabilized silver clusters can be realized on a prototypical scaffold, a DNA nanotube, with attachment sites separated by <10 nm. Cluster attachment is mediated by designed DNA linkers that enable isolation of specific clusters prior to assembly on nanotubes and preserve cluster structure and spectral purity after assembly. The modularity of this approach generalizes to silver clusters of diverse sizes and DNA scaffolds of many types. Thus, these silver cluster nano-optical elements, which themselves have colors selected by their particular DNA templating oligomer, bring unique dimensions of control and flexibility to the rapidly expanding field of nano-optics.

  1. Permanent excimer superstructures by supramolecular networking of metal quantum clusters

    NASA Astrophysics Data System (ADS)

    Santiago-Gonzalez, Beatriz; Monguzzi, Angelo; Azpiroz, Jon Mikel; Prato, Mirko; Erratico, Silvia; Campione, Marcello; Lorenzi, Roberto; Pedrini, Jacopo; Santambrogio, Carlo; Torrente, Yvan; De Angelis, Filippo; Meinardi, Francesco; Brovelli, Sergio

    2016-08-01

    Excimers are evanescent quasi-particles that typically form during collisional intermolecular interactions and exist exclusively for their excited-state lifetime. We exploited the distinctive structure of metal quantum clusters to fabricate permanent excimer-like colloidal superstructures made of ground-state noninteracting gold cores, held together by a network of hydrogen bonds between their capping ligands. This previously unknown aggregation state of matter, studied through spectroscopic experiments and ab initio calculations, conveys the photophysics of excimers into stable nanoparticles, which overcome the intrinsic limitation of excimers in single-particle applications—that is, their nearly zero formation probability in ultra-diluted solutions. In vitro experiments demonstrate the suitability of the superstructures as nonresonant intracellular probes and further reveal their ability to scavenge reactive oxygen species, which enhances their potential as anticytotoxic agents for biomedical applications.

  2. Are the Effects of Structure Formation Seen in the Central Metallicity of Galaxy Clusters?

    NASA Astrophysics Data System (ADS)

    Elkholy, Tamer Y.; Bautz, Mark W.; Canizares, Claude R.

    2015-05-01

    A sample of 46 nearby clusters observed with Chandra is analyzed to produce radial density, temperature, entropy, and metallicity profiles, as well as other morphological measurements. The entropy profiles are computed to larger radii than in previous Chandra cluster sample analyses. We find that the iron mass fraction measured in the inner 0.15{{R}500} shows a larger dispersion across the sample of low-mass clusters than it does for the sample of high-mass clusters. We interpret this finding as the result of the mixing of more halos in large clusters than in small clusters, leading to an averaging of the metallicity in the large clusters, and thus less dispersion of metallicity. This interpretation lends support to the idea that the low-entropy, metal-rich gas of merging halos reaches the clusters’ centers, which explains observations of core-collapse supernova product metallicity peaks, and which is seen in hydrodynamical simulations. The gas in these merging halos would have to reach cluster centers without mixing in the outer regions. On the other hand, the metallicity dispersion does not change with mass in the outer regions of the clusters, suggesting that most of the outer metals originate from a source with a more uniform metallicity level, such as during pre-enrichment. We also measure a correlation between the metal content in low-mass clusters and the morphological disturbance of their intracluster medium, as measured by centroid shift. This suggests an alternative interpretation, whereby transitional metallicity boosts in the center of low-mass clusters account for the larger dispersion of their metallicities.

  3. Targeted Single-Site MOF Node Modification: Trivalent Metal Loading via Atomic Layer Deposition

    SciTech Connect

    Kim, In Soo; Borycz, Joshua; Platero-Prats, Ana E.; Tussupbayev, Samat; Wang, Timothy C.; Farha, Omar K.; Hupp, Joseph T.; Gagliardi, Laura; Chapman, Karena W.; Cramer, Christopher J.; Martinson, Alex B. F.

    2015-07-02

    Postsynthetic functionalization of metal organic frameworks (MOFs) enables the controlled, high-density incorporation of new atoms on a crystallographically precise framework. Leveraging the broad palette of known atomic layer deposition (ALD) chemistries, ALD in MOFs (AIM) is one such targeted approach to construct diverse, highly functional, few-atom clusters. In this paper, we demonstrate the saturating reaction of trimethylindium (InMe3) with the node hydroxyls and ligated water of NU-1000, which takes place without significant loss of MOF crystallinity or internal surface area. We computationally identify the elementary steps by which trimethylated trivalent metal compounds (ALD precursors) react with this Zr-based MOF node to generate a uniform and well characterized new surface layer on the node itself, and we predict a final structure that is fully consistent with experimental X-ray pair distribution function (PDF) analysis. Finally, we further demonstrate tunable metal loading through controlled number density of the reactive handles (–OH and –OH2) achieved through node dehydration at elevated temperatures.

  4. Targeted Single-Site MOF Node Modification: Trivalent Metal Loading via Atomic Layer Deposition

    DOE PAGES

    Kim, In Soo; Borycz, Joshua; Platero-Prats, Ana E.; ...

    2015-07-02

    Postsynthetic functionalization of metal organic frameworks (MOFs) enables the controlled, high-density incorporation of new atoms on a crystallographically precise framework. Leveraging the broad palette of known atomic layer deposition (ALD) chemistries, ALD in MOFs (AIM) is one such targeted approach to construct diverse, highly functional, few-atom clusters. In this paper, we demonstrate the saturating reaction of trimethylindium (InMe3) with the node hydroxyls and ligated water of NU-1000, which takes place without significant loss of MOF crystallinity or internal surface area. We computationally identify the elementary steps by which trimethylated trivalent metal compounds (ALD precursors) react with this Zr-based MOF nodemore » to generate a uniform and well characterized new surface layer on the node itself, and we predict a final structure that is fully consistent with experimental X-ray pair distribution function (PDF) analysis. Finally, we further demonstrate tunable metal loading through controlled number density of the reactive handles (–OH and –OH2) achieved through node dehydration at elevated temperatures.« less

  5. Metal organic chemical vapor deposition of environmental barrier coatings for the inhibition of solid deposit formation from heated jet fuel

    NASA Astrophysics Data System (ADS)

    Mohan, Arun Ram

    Solid deposit formation from jet fuel compromises the fuel handling system of an aviation turbine engine and increases the maintenance downtime of an aircraft. The deposit formation process depends upon the composition of the fuel, the nature of metal surfaces that come in contact with the heated fuel and the operating conditions of the engine. The objective of the study is to investigate the effect of substrate surfaces on the amount and nature of solid deposits in the intermediate regime where both autoxidation and pyrolysis play an important role in deposit formation. A particular focus has been directed to examining the effectiveness of barrier coatings produced by metal organic chemical vapor deposition (MOCVD) on metal surfaces for inhibiting the solid deposit formation from jet fuel degradation. In the first part of the experimental study, a commercial Jet-A sample was stressed in a flow reactor on seven different metal surfaces: AISI316, AISI 321, AISI 304, AISI 347, Inconel 600, Inconel 718, Inconel 750X and FecrAlloy. Examination of deposits by thermal and microscopic analysis shows that the solid deposit formation is influenced by the interaction of organosulfur compounds and autoxidation products with the metal surfaces. The nature of metal sulfides was predicted by Fe-Ni-S ternary phase diagram. Thermal stressing on uncoated surfaces produced coke deposits with varying degree of structural order. They are hydrogen-rich and structurally disordered deposits, spherulitic deposits, small carbon particles with relatively ordered structures and large platelets of ordered carbon structures formed by metal catalysis. In the second part of the study, environmental barrier coatings were deposited on tube surfaces to inhibit solid deposit formation from the heated fuel. A new CVD system was configured by the proper choice of components for mass flow, pressure and temperature control in the reactor. A bubbler was designed to deliver the precursor into the reactor

  6. Entrapment of Metal Clusters in MOF Channels by Extended Hooks Anchored at Open Metal Sites

    PubMed Central

    Zheng, Shou-Tian; Zhao, Xiang; Lau, Samuel; Fuhr, Addis; Feng, Pingyun; Bu, Xianhui

    2015-01-01

    Reported here is a new concept and its practical implementation that involves the novel utilization of open metal sites (OMS) for architectural pore design. Specifically, it is shown here that OMS can be used to run extended hooks (isonicotinate in this work) from the framework wall to channel centers to effect the capture of single metal ions or clusters, with the concurrent partition of the large channel space into multiple domains, alteration of host-guest charge relationship and associated guest-exchange properties, as well as the transfer of OMS from the wall to the channel centers. The concept of the extended hook, demonstrated here in the multi-component dual-metal and dual-ligand system, should be generally applicable to a range of framework types. PMID:23826752

  7. Snow Core Records of Recent Deposition of Trace Metals to Central (Summit) Greenland

    NASA Astrophysics Data System (ADS)

    Shafer, M. M.; Schauer, J. J.; Bergin, M.

    2009-12-01

    later group is representative of the more mobile, anthropogenically dominated trace metals. “Crustal” elements (Al, Ca, Fe, K, Mg, Ti), sulfate (S), and the rare earths present similar profiles, with significant burial peaks in spring. These major burial peaks are uniformly spaced (~70 cm apart), indicating consistency in net snow accumulation rates and transport vectors. A suite of trace elements (Cd, Mn, Ni, P, Pb, Tl, U) exhibit deposition patterns similar to that of the crustals and S. However, the burial patterns of several other elements (Cu, Sn, Zn, oxyanions) were weakly correlated with the crustals and other modes are apparent. The Hg profile exhibits summer peaks and is anti-correlated with most other elements, but is correlated with TOC. TOC and LMWA are, in general though, poorly correlated with most elements, indicating that post-depositional diagenesis may be significant for carbon. A principal component analysis identified four element clusters that appear to be consistent with deposition modalities and element geochemistry, and which explains 71% of total variance.

  8. Electron emission from nanometer-size metallic clusters: Electronic states and structural stability of supported Au clusters

    SciTech Connect

    Lin, M.E.; Ramachandra, A.; Andres, R.P.; Reifenberger, R.

    1992-12-31

    Techniques developed to measure the thermodynamic and electronic properties of a single metallic cluster with nanometer-size dimensions are described. Using these techniques, experiments that resolve the quantized energy spectrum of electrons in a nanometer-size cluster of metallic atoms at room temperature have been performed. Studies on the stability of the electron emission current from an individual nanometer-size cluster supported on a tungsten tip have been performed to learn more about the intrinsic stability of these nanometer-size objects. The data show abrupt jumps between different emission states that are revisited as time progresses. This phenomenon is attributed to a rearrangement of the duster structure and/or orientation on the substrate and provides new evidence of multiple `isomeric` structures for small clusters of metallic atoms.

  9. Cluster Synthesis and Direct Ordering of Rare-Earth Transition-Metal Nanomagnets

    SciTech Connect

    Balasubramanian, B; Skomski, R; Li, XZ; Valloppilly, SR; Shield, JE; Hadjipanayis, GC; Sellmyer, DJ

    2011-04-01

    Rare-earth transition-metal (R-TM) alloys show superior permanent magnetic properties in the bulk, but the synthesis and application of R-TM nanoparticles remains a challenge due to the requirement of high-temperature annealing above about 800 degrees C for alloy formation and subsequent crystalline ordering. Here we report a single-step method to produce highly ordered R-TM nanoparticles such as YCo(5) and Y(2)Co(17), without high-temperature thermal annealing, by employing a cluster-deposition system and investigate their structural and magnetic properties. The direct ordering is highly desirable to create and assemble R-TM nanoparticle building blocks for future permanent-magnet and other significant applications.

  10. Homometallic rare-Earth metal phosphinidene clusters: synthesis and reactivity.

    PubMed

    Wang, Kai; Luo, Gen; Hong, Jianquan; Zhou, Xigeng; Weng, Linhong; Luo, Yi; Zhang, Lixin

    2014-01-20

    Two new trinuclear μ3 -bridged rare-earth metal phosphinidene complexes, [{L(Ln)(μ-Me)}3 (μ3 -Me)(μ3 -PPh)] (L=[PhC(NC6 H4 iPr2 -2,6)2 ](-) , Ln=Y (2 a), Lu (2 b)), were synthesized through methane elimination of the corresponding carbene precursors with phenylphosphine. Heating a toluene solution of 2 at 120 °C leads to an unprecedented ortho CH bond activation of the PhP ligand to form the bridged phosphinidene/phenyl complexes. Reactions of 2 with ketones, thione, or isothiocyanate show clear phospha-Wittig chemistry, giving the corresponding organic phosphinidenation products and oxide (sulfide) complexes. Reaction of 2 with CS2 leads to the formation of novel trinuclear rare-earth metal thione dianion clusters, for which a possible pathway was determined by DFT calculation. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Emission FTIR analyses of thin microscopic patches of jet fuel residue deposited on heated metal surface

    NASA Technical Reports Server (NTRS)

    Lauer, J. L.; Vogel, P.

    1984-01-01

    Deposits laid down in patches on metal strips in a high pressure/high temperature fuel system simulator operated with aerated fuel at varying flow rates were analyzed by emission FTIR in terms of functional groups. Significant differences were found in the spectra and amounts of deposits derived from fuels to which small concentrations of oxygen-, nitrogen-, or sulfur-containing heterocyclics or metal naphthenates were added. The spectra of deposits generated on strips by heating fuels and air in a closed container were very different from those of the flowing fluid deposits. One such closed-container dodecane deposit on silver gave a strong surface-enhanced Raman spectrum.

  12. Structure and mobility of metal clusters in MOFs: Au, Pd, and AuPd clusters in MOF-74.

    PubMed

    Vilhelmsen, Lasse B; Walton, Krista S; Sholl, David S

    2012-08-01

    Understanding the adsorption and mobility of metal-organic framework (MOF)-supported metal nanoclusters is critical to the development of these catalytic materials. We present the first theoretical investigation of Au-, Pd-, and AuPd-supported clusters in a MOF, namely MOF-74. We combine density functional theory (DFT) calculations with a genetic algorithm (GA) to reliably predict the structure of the adsorbed clusters. This approach allows comparison of hundreds of adsorbed configurations for each cluster. From the investigation of Au(8), Pd(8), and Au(4)Pd(4) we find that the organic part of the MOF is just as important for nanocluster adsorption as open Zn or Mg metal sites. Using the large number of clusters generated by the GA, we developed a systematic method for predicting the mobility of adsorbed clusters. Through the investigation of diffusion paths a relationship between the cluster's adsorption energy and diffusion barrier is established, confirming that Au clusters are highly mobile in the MOF-74 framework and Pd clusters are less mobile.

  13. Critical field of two-dimensional superconducting Sn1-x/Six bimetallic composite cluster assembled films with energetic cluster impact deposition

    NASA Astrophysics Data System (ADS)

    Kurokawa, Yuichiro; Hihara, Takehiko; Ichinose, Ikuo

    2013-05-01

    Sn1-x/Six cluster assembled films have been prepared by an energetic cluster impact deposition using a plasma-gas-condensation cluster beam deposition apparatus. Transmission electron microscope images indicated that individual clusters have composite morphologies, where Sn and Si were separated from each other. The superconducting critical magnetic fields, Hc, of Sn1-x/Six cluster assembled films were measured and found to be much higher than the critical magnetic field of the bulk Sn. We estimated the Hc values by using a theory of the superconducting thin film. The estimated values are in good agreement with the experiments, indicating that the Sn1-x/Six cluster assembled films can be regarded as a two-dimensional system although thickness, t, of Sn1-x/Six cluster assembled films (t ≈ 1000 nm) is thicker than conventional superconducting thin film (t < 100 nm).

  14. Regional trends in soil acidification and exchangeable metal concentrations in relation to acid deposition rates.

    PubMed

    Stevens, Carly J; Dise, Nancy B; Gowing, David J

    2009-01-01

    The deposition of high levels of reactive nitrogen (N) and sulphur (S), or the legacy of that deposition, remain among the world's most important environmental problems. Although regional impacts of acid deposition in aquatic ecosystems have been well documented, quantitative evidence of wide-scale impacts on terrestrial ecosystems is not common. In this study we analysed surface and subsoil chemistry of 68 acid grassland sites across the UK along a gradient of acid deposition, and statistically related the concentrations of exchangeable soil metals (1 M KCl extraction) to a range of potential drivers. The deposition of N, S or acid deposition was the primary correlate for 8 of 13 exchangeable metals measured in the topsoil and 5 of 14 exchangeable metals in the subsoil. In particular, exchangeable aluminium and lead both show increased levels above a soil pH threshold of about 4.5, strongly related to the deposition flux of acid compounds.

  15. Deposition of heavy metals from particulate settleable matter in soils of an industrialized area

    NASA Astrophysics Data System (ADS)

    Sanfeliu, Teófilo

    2010-05-01

    Particulate air pollutants from industrial emissions and natural resource exploitation represent an important contribution to soil contamination. These atmospheric particles, usually settleable particulate matter form (which settle by gravity) are deposited on soil through both dry and wet. The most direct consequences on soil of air pollutants are acidification and salinization, not to mention the pollution that can cause heavy metals as components of suspended particulate matter. The main objective of this study was to evaluate the influence of air pollution in soil composition. For this purpose, has been conducted a study of the composition of heavy metals in the settleable particulate matter in two locations (Almazora and Vila-real) with high industrial density (mainly ceramic companies) located in the ceramic cluster of Castellón (Spain). Settleable air particles samples were collected with a PS Standard Britannic captor (MCV-PS2) for monthly periods between January 2007 and December 2009. We analyzed the following elements: Cd, Pb, Cu, Ni, Sb and Bi which are highly toxic and have the property of accumulating in living organisms. It has been determined the concentration of heavy metals in the soluble fraction of settleable air particles by ICP-MS. The annual variation of the results obtained in both populations shows a decline over the study period the concentrations of heavy metals analyzed. This fact is associated with the steady implementation of corrective measures in the main industrial sector in the area based on the treatment of mineral raw materials. Moreover, this decline is, in turn, a lower intake of heavy metals to the soil. REFERENCES Gómez E.T.; Sanfeliu T.; Rius J.; Jordán M.M. (2005) "Evolution, sources and distribution of mineral particles and amorphous phase of atmospheric aerosol in an industrial and Mediterranean coastal area" Water, air and Soil Pollution 167:311-330 Moral R., Gilkes R.J.; Jordán M.M. (2005) "Distribution of heavy

  16. X-Ray Standing Wave Studies of Underpotentially Deposited Metal Monolayers

    DTIC Science & Technology

    1992-01-01

    DTIC E, ELECTE FEB 02 1994 N - X-ray Standing Wave Studies of Underpotentially Deposited Metal Monolayers G. M. Bommarito, D. Acevedo, J. F... underpotentially deposited (UPD) copper on an iodine covered platinum surface and of copper on a Au(100) single crystal electrode. For Cu UPD on Pt, surface...INTRODUCTION 4• The process of underpotential deposition (UPD) of metals has been extensively I studied during the past two decades due to its

  17. Solution synthesis of mixed-metal chalcogenide nanoparticles and spray deposition of precursor films

    DOEpatents

    Schulz, Douglas L.; Curtis, Calvin J.; Ginley, David S.

    2000-01-01

    A colloidal suspension comprising metal chalcogenide nanoparticles and a volatile capping agent. The colloidal suspension is made by reacting a metal salt with a chalcogenide salt in an organic solvent to precipitate a metal chalcogenide, recovering the metal chalcogenide, and admixing the metal chalcogenide with a volatile capping agent. The colloidal suspension is spray deposited onto a substrate to produce a semiconductor precursor film which is substantially free of impurities.

  18. Heavy metals in particulate and colloidal matter from atmospheric deposition of urban Guangzhou, South China.

    PubMed

    Huang, Wen; Duan, Dandan; Zhang, Yulong; Cheng, Hefa; Ran, Yong

    2014-08-30

    Suspended particulate matter (SPM) and colloidal matter (COM) in annual dry and wet deposition samples in urban Guangzhou were for the first time collected, and their trace metals were investigated by using inductively coupled plasma mass spectrometry (ICP-MS). The deposition flux of SPM and of metal elements varied largely among the investigated seasons, and reached the maximum in spring. The correlation analysis indicated that significant correlations existed among some of the metal elements in the deposition samples. The enrichment factors (EF) of metals in COM in the deposition ranging from 79.66 to 130,000 were much higher than those of SPM ranging from 1.65 to 286.48, indicating the important role of COM. The factor analysis showed that emissions from street dust, non-ferrous metal production, and heavy fuel oil were major sources of the trace metals. Positive matrix factorization (PMF) model was used to quantitatively estimate anthropogenic source.

  19. Structural, electronic and magnetic properties of binary transition metal aluminum clusters: absence of electronic shell structure.

    PubMed

    Chauhan, Vikas; Singh, Akansha; Majumder, Chiranjib; Sen, Prasenjit

    2014-01-08

    Single Cr, Mn, Fe, Co and Ni doped Al clusters having up to 12 Al atoms are studied using density functional methods. The global minima of structure for all the clusters are identified, and their relative stability and electronic and magnetic properties are studied. FeAl4 and CoAl3 are found to have enhanced stability and aromatic behavior. In contrast to binary transition metal alkali and transition metal alkaline earth clusters, spherical shell models cannot describe the electronic structure of transition metal aluminum clusters.

  20. Solution-based deposition of ultrathin metal oxide films on metal and superconductor surfaces

    NASA Astrophysics Data System (ADS)

    Westwood, Glenn

    Solution chemical methods were used to deposit ultrathin metal oxide films on metal and superconductor surfaces. Platinum-molybdenum oxide films were deposited by spontaneous adsorption and electrodeposition of hexamolybdoplatinate, PtMO6O248-. Spectroscopic characterization by 17O and 195Pt NMR showed that the PtMo6O248- anion is stable in aqueous solution below pH 4. The interaction of this solution stable anion with Au and Ag was characterized by in situ scanning tunneling microscopy, x-ray photoelectron spectroscopy, and cyclic voltammetry. The anion was partially reduced upon adsorption on Ag, but spontaneously adsorbed on Au to form an amorphous surface phase. The electrodeposition of hexamolybdoplatinate on Au electrodes resulted in an electrode surface that was different from the spontaneously adsorbed species, in terms of composition, voltammetry, and reactivity. Cyclic voltammetry was also used to compare the reactivity of these materials for the electrooxidation of methanol. Ultrathin zirconia films were deposited on YBa2Cu3O 7-delta by alternating exposures to tetra n-propyl zirconate, Zr4(OPrn)16, and H2O in n-propanol. Physical and chemical characterization of these films was done by x-ray photoelectron spectroscopy, atomic force microscopy, and cross-section transmission electron microscopy. The zirconia films were determined to be ultrathin (<10 nm) and highly conformal to the surface of YBa2Cu3O7-delta. Metal-insulator-superconductor tunnel junctions fabricated in this fashion were characterized by current-voltage and conductivity-voltage measurements. Solution deposition from Zr4(OPrn) 16 was also used to deposit ultrathin zirconia films on gold, silver, and aluminum surfaces. X-ray photoelectron spectroscopy and atomic force microscopy were used to compare the physical properties of these films. Electrical measurements showed that zirconia films on Ag and Au are not insulating, but aluminum-zirconia-aluminum capacitors fabricated by this method

  1. Glass surface metal deposition with high-power femtosecond fiber laser

    NASA Astrophysics Data System (ADS)

    Liu, Jian; Deng, Cheng; Bai, Shuang

    2016-12-01

    Using femtosecond fiber laser-based additive manufacturing (AM), metal powder is deposited on glass surface for the first time to change its surface reflection and diffuse its transmission beam. The challenge, due to mismatch between metal and glass on melting temperature, thermal expansion coefficient, brittleness, is resolved by controlling AM parameters such as power, scan speed, hatching, and powder thickness. Metal powder such as iron is successfully deposited and demonstrated functions such as diffusion of light and blackening effects.

  2. Conical octopole ion guide: Design, focusing, and its application to the deposition of low energetic clusters

    SciTech Connect

    Roettgen, Martin A.; Judai, Ken; Antonietti, Jean-Marie; Heiz, Ueli; Rauschenbach, Stephan; Kern, Klaus

    2006-01-15

    A design of a radio-frequency (rf) octopole ion guide with truncated conical rods arranged in a conical geometry is presented. The performance is tested in a cluster deposition apparatus used for the soft-landing of size-selected clusters on well-characterized substrates used as a model system in heterogeneous catalysis in ultrahigh vacuum. This device allows us to focus 500 pA of a mass-selected Ni{sub 20}{sup +} cluster ion beam from 9 mm down to a spot size of 2 mm in diameter. The transmittance is 70%{+-}5% at a rf voltage of 420 V{sub pp} applied over an amateur radio transceiver with an interposed homemade amplifier-transformer circuit. An increase of the cluster density by a factor of 15 has been achieved. Three ion trajectories are simulated by using SIMION6, which are relevant for this focusing device: transmitted, reflected, and absorbed. The observed effects in the simulations can be successfully explained by the adiabatic approximation. The focusing behavior of the conical octopole lens is demonstrated by experiment and simulations to be a very useful technique for increasing molecule or cluster densities on a substrate and thus reducing deposition time.

  3. Hydrogen mimicking the properties of coinage metal atoms in Cu and Ag monohydride clusters.

    PubMed

    Vetter, Karsten; Proch, Sebastian; Ganteför, Gerd F; Behera, Swayamprabha; Jena, Puru

    2013-12-28

    A systematic study of the electronic structure and equilibrium geometries of Cun, Cun-1H, Agn, and Agn-1H; n = 2-5 clusters is carried out using photoelectron spectroscopy (PES) experiments and density functional theory based calculations. Our objective is to see if the substitution of a coinage metal atom by hydrogen would retain the electronic structure of the parent metal cluster since both systems are isoelectronic. For clusters with n ≥ 3, we find that the measured PES and vertical detachment energies (VDEs) (i.e. energies necessary to remove an electron from the anionic Mn(-) (M = Cu, Ag) clusters without changing their geometries) are close to those of Mn-1H(-) clusters, suggesting that substitution of a metal atom with hydrogen does not perturb the electronic structure of the parent cluster anion significantly. Calculated VDEs agree very well with experiment validating the theoretical methods used as well as the geometries of the neutral and anionic clusters.

  4. Formation of metallic magnetic clusters in a Kondo-lattice metal: evidence from an optical study.

    PubMed

    Kovaleva, N N; Kugel, K I; Bazhenov, A V; Fursova, T N; Löser, W; Xu, Y; Behr, G; Kusmartsev, F V

    2012-01-01

    Magnetic materials are usually divided into two classes: those with localised magnetic moments, and those with itinerant charge carriers. We present a comprehensive experimental (spectroscopic ellipsomerty) and theoretical study to demonstrate that these two types of magnetism do not only coexist but complement each other in the Kondo-lattice metal, Tb(2)PdSi(3). In this material the itinerant charge carriers interact with large localised magnetic moments of Tb(4f) states, forming complex magnetic lattices at low temperatures, which we associate with self-organisation of magnetic clusters. The formation of magnetic clusters results in low-energy optical spectral weight shifts, which correspond to opening of the pseudogap in the conduction band of the itinerant charge carriers and development of the low- and high-spin intersite electronic transitions. This phenomenon, driven by self-trapping of electrons by magnetic fluctuations, could be common in correlated metals, including besides Kondo-lattice metals, Fe-based and cuprate superconductors.

  5. Formation of metallic magnetic clusters in a Kondo-lattice metal: Evidence from an optical study

    NASA Astrophysics Data System (ADS)

    Kovaleva, N. N.; Kugel, K. I.; Bazhenov, A. V.; Fursova, T. N.; Löser, W.; Xu, Y.; Behr, G.; Kusmartsev, F. V.

    2012-11-01

    Magnetic materials are usually divided into two classes: those with localised magnetic moments, and those with itinerant charge carriers. We present a comprehensive experimental (spectroscopic ellipsomerty) and theoretical study to demonstrate that these two types of magnetism do not only coexist but complement each other in the Kondo-lattice metal, Tb2PdSi3. In this material the itinerant charge carriers interact with large localised magnetic moments of Tb(4f) states, forming complex magnetic lattices at low temperatures, which we associate with self-organisation of magnetic clusters. The formation of magnetic clusters results in low-energy optical spectral weight shifts, which correspond to opening of the pseudogap in the conduction band of the itinerant charge carriers and development of the low- and high-spin intersite electronic transitions. This phenomenon, driven by self-trapping of electrons by magnetic fluctuations, could be common in correlated metals, including besides Kondo-lattice metals, Fe-based and cuprate superconductors.

  6. Formation of metallic magnetic clusters in a Kondo-lattice metal: Evidence from an optical study

    PubMed Central

    Kovaleva, N. N.; Kugel, K. I.; Bazhenov, A. V.; Fursova, T. N.; Löser, W.; Xu, Y.; Behr, G.; Kusmartsev, F. V.

    2012-01-01

    Magnetic materials are usually divided into two classes: those with localised magnetic moments, and those with itinerant charge carriers. We present a comprehensive experimental (spectroscopic ellipsomerty) and theoretical study to demonstrate that these two types of magnetism do not only coexist but complement each other in the Kondo-lattice metal, Tb2PdSi3. In this material the itinerant charge carriers interact with large localised magnetic moments of Tb(4f) states, forming complex magnetic lattices at low temperatures, which we associate with self-organisation of magnetic clusters. The formation of magnetic clusters results in low-energy optical spectral weight shifts, which correspond to opening of the pseudogap in the conduction band of the itinerant charge carriers and development of the low- and high-spin intersite electronic transitions. This phenomenon, driven by self-trapping of electrons by magnetic fluctuations, could be common in correlated metals, including besides Kondo-lattice metals, Fe-based and cuprate superconductors. PMID:23189239

  7. Assessment of PM10 and heavy metals concentration in a Ceramic Cluster (NE Spain)

    NASA Astrophysics Data System (ADS)

    Belen Vicente, Ana; Pardo, Francisco; Sanfeliu, Teofilo; Bech, Joan

    2013-04-01

    Environmental pollution control is one of the most important goals in pollution risk assessment today. The aim of this study is conducting a retrospective view of the evolution of particulate matter (PM10) and heavy metals (As, Cd, Ni and Pb) at different localities in the Spanish cluster ceramic in the period between January 2007 and December 2011. The study area is in the province of Castellón. This province is a strategical area in the framework of European Union Pollution control. Approximately 80% of European ceramic tiles and ceramic frits manufacturers are concentrated in two areas, forming the so-called "Ceramics Clusters"; one is in Modena (Italy) and the other in Castellón (Spain). In this kind of areas, there are a lot of pollutants from this industry that represent an important contribution to soil contamination so it is necessary to control the air quality in them. These atmospheric particles are deposited in the ground through both dry and wet deposition. Soil is a major sink for heavy metals released into the environment. The level of pollution of soils by heavy metals depends on the retention capacity of the soil, especially on physical-chemical properties (mineralogy, grain size, organic matter) affecting soil particle surfaces and also on the chemical properties of the metal. The most direct consequences on the ground of air pollutants are acidification, salinization and the pollutions that can cause heavy metals as components of suspended particulate matter. For this purpose the levels of PM10 in ambient air and the corresponding annual and weekly trend were calculated. The results of the study show that the PM10 and heavy metals concentrations are below the limit values recommended by European Union Legislation for the protection of human health and ecosystems in the study period. There is an important reduction of them from 2009 in all control stations due to the economic crisis. References Moral, R., Gilkes, R.J., Jordán, M.M., 2005

  8. Investigation of Metal Free Naphthalocyanine Vapor Deposited on Au(111)

    SciTech Connect

    Wiggins, Bryan C.; Hipps, Kerry W.

    2014-02-27

    Naphthalocyanines (Ncs) are promising candidates for future components in electronic devices and applications. To maximize the efficiency of Nc devices, it is critical to understand their structural and electronic properties and how these are impacted by deposition methods. The formation of a metal free naphthalocyanine (H2Nc) self-assembled monolayer on a Au(111) crystal was investigated by scanning tunneling microscopy under ultra-high-vacuum conditions at room temperature. A rigorous purification and processing procedure was developed to produce high purity, low defect, and well-ordered monolayers. High-resolution STM images reveal epitaxial growth of H2Nc on Au(111) with the observed structure having a molecular spacing of 1.6 ± 0.05 nm, with molecules orientated slightly off (roughly 2.5°) the low density packing direction of Au(111). A commensurate structure having 4 molecules per unit cell and unit cell parameters of A = 3.25 ± 0.05 nm, B = 3.17 ± 0.05 nm, and α = 87.5 ± 2° is proposed. Orbital-mediated tunneling spectroscopy was used to examine the electronic properties of individual molecules within the thin film. The first ionization potential and electron affinity of H2Nc adsorbed on Au(111) were measured to be -0.68 ± 0.03 and 1.12 ± 0.02 eV, relative to the Fermi energy.

  9. Porosity formation and gas bubble retention in laser metal deposition

    NASA Astrophysics Data System (ADS)

    Ng, G. K. L.; Jarfors, A. E. W.; Bi, G.; Zheng, H. Y.

    2009-11-01

    One of the inherent problems associated with laser metal deposition using gas-assisted powder transfer is the formation of porosity, which can be detrimental to the mechanical properties of the bulk material. In this work, a comprehensive investigation of porosity is carried out using gas atomised Inconel 718 powder. In the analysis, a clear distinction is made between two types of porosity; namely lack of fusion and gas porosity. The results show that the two types of porosity are attributed by different factors. The gas porosity, which is more difficult to eliminate than the lack of fusion, can be as high as 0.7%. The study shows that the gas porosity is dependent on the process parameters and the melt pool dynamics. The flotation of entrapped gas bubbles was analysed, showing that in a stationary melt pool the gas would be retained by Marangoni-driven flow. The overall Marangoni-driven flow of the melt pool is in the order of five times higher than the flotation effect, and this is the reason why the melt pool geometry would tend to dominate the flow direction of the gas bubbles. Through optimisation, the gas porosity can be reduced to 0.037%.

  10. Pal 12 - A metal-rich globular cluster in the outer halo

    NASA Technical Reports Server (NTRS)

    Cohen, J. G.; Frogel, J. A.; Persson, S. E.; Zinn, R.

    1980-01-01

    New optical and infrared observations of several stars in the distant globular cluster Pal 12 show that they have CO strengths and heavy element abundances only slightly less than in M 71, one of the more metal-rich globular clusters. Pal 12 thus has a metal abundance near the high end of the range over which globular clusters exist and lies in the outer galactic halo. Its red horizontal branch is not anomalous in view of the abundance that has been found.

  11. Pal 12 - A metal-rich globular cluster in the outer halo

    NASA Technical Reports Server (NTRS)

    Cohen, J. G.; Frogel, J. A.; Persson, S. E.; Zinn, R.

    1980-01-01

    New optical and infrared observations of several stars in the distant globular cluster Pal 12 show that they have CO strengths and heavy element abundances only slightly less than in M 71, one of the more metal-rich globular clusters. Pal 12 thus has a metal abundance near the high end of the range over which globular clusters exist and lies in the outer galactic halo. Its red horizontal branch is not anomalous in view of the abundance that has been found.

  12. Surface modification of metal and metal coated nanoparticles to induce clustering

    NASA Astrophysics Data System (ADS)

    Gowda, M. H.; Glembocki, O. J.; Geng, S.; Prokes, S. M.; Garces, N.; Caldwell, J. D.

    2010-08-01

    Surface enhanced Raman scattering (SERS) is a powerful technique for the detection of submonolayer coverage of gold or silver surfaces. The magnitude of the effect and the spectral wavelength of the peak depend on the metal nanoparticles used and its geometry. In this paper we show that the use of chemicals that bind to gold or silver can lead to the clustering of nanoparticles. We used well defined Au nanoparticles in our experiments and add cysteamine to solutions containing the nanoparticles. The plasmonic response of the nanoparticles is measured by transmission Surface Plasmon Resonance (SPR) spectroscopy. We observed significant changes to the SPR spectra that are characteristics of close coupled nanoparticles. The time evolution of these changes indicates the formation of gold nanoparticles clusters. The SERS response of these clustered nanoparticles is observed to red shift from the designed peak wavelength in the green to the red. In addition, the placement of these clusters on dielectric surfaces shifts the SPR even more into the red. The experimental results are supported by calculations of the electromagnetic fields using finite difference methods.

  13. Dry deposition of airborne trace metals on the Los Angeles Basin and adjacent coastal waters

    NASA Astrophysics Data System (ADS)

    Lu, R.; Turco, R. P.; Stolzenbach, K.; Friedlander, S. K.; Xiong, C.; Schiff, K.; Tiefenthaler, L.; Wang, Guangyu

    2003-01-01

    We present an assessment of the deposition rates of airborne trace metals onto the Los Angeles Basin and adjacent coastal waters. For this purpose, the UCLA Surface Meteorology and Ozone Generation (SMOG) air pollution modeling system has been used to simulate the geographical distributions of trace metals and their deposition fluxes. Calculations were performed for average summer and winter conditions, as well as for extreme meteorological events, in particular, for Santa Ana winds. Thus, a series of simulations were carried out that define the range of meteorological conditions contributing to dry deposition in the region. These predictions have been calibrated and validated using measurements collected in the LA area. Significant spatial and temporal variability are found in trace metal concentrations and deposition rates. Large spatial gradients occur near the coast as well as at the mountainous boundaries of the airshed. Considerable diurnal and seasonal variations in trace metal deposition are also noted. For example, the development of a daytime sea breeze, particularly in the warmer months, leads to greater deposition in the northern and eastern basin as well as in the high desert. A nighttime land breeze, especially in the colder months, enhances deposition onto coastal ocean surfaces. Large particles dominate local trace metal deposition in central urban (and adjacent) areas, while fine particles export metals over regional scales through long-range advection. Since the majority of urban metal deposition occurs on particles larger than 10-μm diameter, routine measurements of PM10 or PM2.5 concentrations for air quality characterization may not be reliable indicators of local sources. Some 35-45% of all trace metal emissions are deposited locally within the Los Angeles Basin on an annual basis. Santa Monica Bay and its watersheds receive about 6% of this amount, which can have a significant impact on trace metal concentrations in the surface waters of the

  14. Assessment of atmospheric heavy metal deposition in the Tarkwa gold mining area of Ghana using epiphytic lichens

    NASA Astrophysics Data System (ADS)

    Boamponsem, L. K.; Adam, J. I.; Dampare, S. B.; Nyarko, B. J. B.; Essumang, D. K.

    2010-05-01

    In situ lichens ( Parmelia sulcata) have been used to assess atmospheric heavy metal deposition in the Tarkwa gold mining area of Ghana. Total heavy metal concentrations obtained by instrumental neutron activation analysis (INAA) were processed by positive matrix factorization (PMF), principal component (PCA) and cluster (CA) analyses. The pollution index factor (PIF) and pollution load index (PLI) criteria revealed elevated levels of Sb, Mn, Cu, V, Al, Co, Hg, Cd and As in excess of the background values. The PCA and CA classified the examined elements into anthropogenic and natural sources, and PMF resolved three primary sources/factors: agricultural activities and other non-point anthropogenic origins, natural soil dust, and gold mining activities. Gold mining activities, which are characterized by dominant species of Sb, Th, As, Hg, Cd and Co, and significant contributions of Cu, Al, Mn and V, are the main contributors of heavy metals in the atmosphere of the study area.

  15. Laser Spectroscopy of Small Mass Selected Metal Clusters and Complexes

    NASA Astrophysics Data System (ADS)

    Robbins, David Lee

    1995-01-01

    been reported and furthermore no other metal dimer-ligand complex had been reported prior to these studies. The metal dimer work is relevant to surface adsorption and catalysis and represents the simplest adsorption experiment to date, that is adsorption of a ligand on the smallest metal cluster surface. The Mg^+ -N_2 study along with other recently investigated ion-molecule complexes are the first such complexes to be investigated.

  16. Microfluidic Patterning of Metal Structures for Flexible Conductors by In Situ Polymer-Assisted Electroless Deposition.

    PubMed

    Liang, Suqing; Li, Yaoyao; Zhou, Tingjiao; Yang, Jinbin; Zhou, Xiaohu; Zhu, Taipeng; Huang, Junqiao; Zhu, Julie; Zhu, Deyong; Liu, Yizhen; He, Chuanxin; Zhang, Junmin; Zhou, Xuechang

    2017-02-01

    A low-cost, solution-processed, versatile, microfluidic approach is developed for patterning structures of highly conductive metals (e.g., copper, silver, and nickel) on chemically modified flexible polyethylene terephthalate thin films by in situ polymer-assisted electroless metal deposition. This method has significantly lowered the consumption of catalyst as well as the metal plating solution.

  17. Origin of Selective Adsorption for Metal Nano-clusters on Graphene/Ru(0001)

    NASA Astrophysics Data System (ADS)

    Zhang, Lizhi; Sun, Jiatao; Huang, Li; Pan, Lida; Du, Shixuan; Gao, Hongjun

    2013-03-01

    These years, metal nano-clusters have attracted many interests because of their exciting properties and the potential applications in the catalysis industries, the information storage and so on. Recently, many groups composed the homogenous and size-controlled metal nano-clusters on graphene/Ru(0001) moiré template (G/Ru(0001)). However, the growth modes of these nano-clusters are not very clear. Here, we investigated the mechanism of selective adsorption of some transition metal (TM) atoms on G/Ru(0001) by DFT calculations, and proposed a criterion to estimate the growth mode of TM atoms on G/Ru(0001). We found that both the intensity of sp3 hybridization of carbon atoms in different regions of G/Ru(0001) and the electronic structure of the transition metal atoms influence the adsorption site and the selectivity of metal atoms on G/Ru(0001) at initio stage. According to the electronic structures of some other different G/metal systems, we also predicted that some other G/metal templates can be used to grow the metal nano-clusters. The growth mechanism agrees well with the experimental observations, and provides a way to select suitable metal atoms to form dispersed metal nano-clusters on the G/metal template.

  18. Processing Parameters Optimization for Material Deposition Efficiency in Laser Metal Deposited Titanium Alloy

    NASA Astrophysics Data System (ADS)

    Mahamood, Rasheedat M.; Akinlabi, Esther T.

    2016-03-01

    Ti6Al4V is an important Titanium alloy that is mostly used in many applications such as: aerospace, petrochemical and medicine. The excellent corrosion resistance property, the high strength to weight ratio and the retention of properties at high temperature makes them to be favoured in most applications. The high cost of Titanium and its alloys makes their use to be prohibitive in some applications. Ti6Al4V can be cladded on a less expensive material such as steel, thereby reducing cost and providing excellent properties. Laser Metal Deposition (LMD) process, an additive manufacturing process is capable of producing complex part directly from the 3-D CAD model of the part and it also has the capability of handling multiple materials. Processing parameters play an important role in LMD process and in order to achieve desired results at a minimum cost, then the processing parameters need to be properly controlled. This paper investigates the role of processing parameters: laser power, scanning speed, powder flow rate and gas flow rate, on the material utilization efficiency in laser metal deposited Ti6Al4V. A two-level full factorial design of experiment was used in this investigation, to be able to understand the processing parameters that are most significant as well as the interactions among these processing parameters. Four process parameters were used, each with upper and lower settings which results in a combination of sixteen experiments. The laser power settings used was 1.8 and 3 kW, the scanning speed was 0.05 and 0.1 m/s, the powder flow rate was 2 and 4 g/min and the gas flow rate was 2 and 4 l/min. The experiments were designed and analyzed using Design Expert 8 software. The software was used to generate the optimized process parameters which were found to be laser power of 3.2 kW, scanning speed of 0.06 m/s, powder flow rate of 2 g/min and gas flow rate of 3 l/min.

  19. Influence of the cluster orientation on the epitaxy: deposition of Co nanoclusters on Cu(001) surfaces.

    PubMed

    Jiménez-Sáez, J C; Ettaoussi, M S; Pérez-Martín, A M C; Kerkeb, M L; Jiménez-Rodríguez, J J

    2010-02-01

    Deposition at low energy of 147-atom icosahedral Co nanoclusters on Cu(001) substrates is studied by molecular-dynamics simulations. Atomic interactions were mimicked by a many-body potential based on the tight-binding second-moment approximation. Clusters were rotated by using the two first Euler angles, in the so-called "x-convention," and subsequently, they were deposited on the substrate. The dependence of the degree of epitaxy on these angles has been obtained. Epitaxy is also related to the initial number of (001)-oriented atoms, especially for extreme values of this latter quantity. A better epitaxial matching is connected with a larger spreading index. The explanation of the epitaxial behavior of the supported clusters resides mainly in the dynamical interaction between grains during approximately the first 40 ps. Whenever the newly-formed (001)-oriented grain competes against a large number of grains after the collision, a very low epitaxial matching is obtained.

  20. Laser-induced metal plasmas for pulsed laser deposition of metal-oxide thin films

    NASA Astrophysics Data System (ADS)

    Wagenaars, Erik; Colgan, James; Rajendiran, Sudha; Rossall, Andrew

    2015-09-01

    Metal and metal-oxide thin films, e.g. ZnO, MgO, Al2O3 and TiO2, are widely used in e.g. microelectronics, catalysts, photonics and displays. Pulsed Laser Deposition (PLD) is a plasma-based thin-film deposition technique that is highly versatile and fast, however it suffers from limitations in control of film quality due to a lack of fundamental understanding of the underlying physical processes. We present experimental and modelling studies of the initial phases of PLD: laser ablation and plume expansion. A 2D hydrodynamic code, POLLUX, is used to model the laser-solid interaction of a Zn ablation with a Nd:YAG laser. In this early phase of PLD, the plasma plume has temperatures of about 10 eV, is highly ionized, and travels with a velocity of about 10-100 km/sec away from the target. Subsequently, the plasma enters the plume expansion phase in which the plasma cools down and collision chemistry changes the composition of the plume. Time-integrated optical emission spectroscopy shows that Zn I and Zn II emission lines dominate the visible range of the light emission. Comparison with the Los Alamos plasma kinetics code ATOMIC shows an average temperature around 1 eV, indicating a significant drop in plasma temperature during the expansion phase. We acknowledge support from the UK Engineering and Physical Sciences Research Council (EPSRC), Grant EP/K018388/1.

  1. Assessment of toxicity in waters due to heavy metals derived from atmospheric deposition using Vibrio fischeri.

    PubMed

    Cukurluoglu, Sibel; Muezzinoglu, Aysen

    2013-01-01

    Water toxicity originating from the atmospheric deposition of six heavy metals (Cd, Cr, Cu, Ni, Pb, Zn) was investigated on Vibrio fischeri activity in Izmir, Turkey. A LUMIStox® test was applied to dry and wet deposition samples and metal solutions. The inhibition levels and effective toxicity concentrations of these samples and solutions were determined. Interactive toxicity effects among the metals were investigated. When the impacts of the synthetic single heavy metal solutions were compared with each other, a toxicity ranking of Cr>Cd>Pb>Cu>Zn>Ni was obtained in order of decreasing severity. The total effective concentrations of these six metals were in the ranges of 0.074-0.221 mg/L and 0.071-0.225 mg/L for receiving aqueous solutions of dry and wet atmospheric depositions, respectively. The toxicity data showed that the wet deposition samples were 15% more toxic than the dry deposition samples. The interactive toxicity effects of the heavy metals in both dry and wet deposition samples were classified as antagonistic. High levels of heavy metals deposited in dissolved form may constitute an important input in the biochemical cycle and may have significant impacts.

  2. Dry deposition and resuspension of particle-associated metals near a freeway in Los Angeles

    NASA Astrophysics Data System (ADS)

    Sabin, Lisa D.; Hee Lim, Jeong; Teresa Venezia, Maria; Winer, Arthur M.; Schiff, Kenneth C.; Stolzenbach, Keith D.

    Dry atmospheric deposition represents a potentially large source of pollutant metal contamination in urban stormwater runoff, yet there is a limited amount of research on the relationship between atmospheric emissions and water quality problems in urban areas. In Los Angeles, with air quality that ranks among the worst in the United States, significant quantities of toxic materials are released into the atmosphere every day, and paved road dust represents the largest source of particle-associated metal emissions to the atmosphere. In order to better understand the role of roadways as a source of localized metal deposition, we characterized the horizontal dry deposition patterns of chromium, copper, lead, nickel and zinc upwind and at increasing distances downwind of the I-405 Freeway in coastal Los Angeles. Dry deposition fluxes and atmospheric concentrations of these metals were highest at the site closest to the freeway, and reduced to approximately urban background concentrations between 10 and 150 m downwind of the freeway. Compared with urban background, atmospheric particle size distributions indicated the freeway was a significant source of these metals on large particles >6 μm in diameter, which deposit close to their source and account for the increased dry deposition flux rates observed near the freeway. The spatial pattern of measured deposition flux was well predicted by a relatively simple line-source Gaussian plume model modified to include particle deposition and resuspension. The model results indicated dilution by vertical dispersion of the plume was the most important mechanism regulating downwind concentrations and deposition.

  3. The SLUGGS survey: calcium triplet-based spectroscopic metallicities for over 900 globular clusters

    NASA Astrophysics Data System (ADS)

    Usher, Christopher; Forbes, Duncan A.; Brodie, Jean P.; Foster, Caroline; Spitler, Lee R.; Arnold, Jacob A.; Romanowsky, Aaron J.; Strader, Jay; Pota, Vincenzo

    2012-10-01

    Although the colour distribution of globular clusters in massive galaxies is well known to be bimodal, the spectroscopic metallicity distribution has been measured in only a few galaxies. After redefining the calcium triplet index-metallicity relation, we use our relation to derive the metallicity of 903 globular clusters in 11 early-type galaxies. This is the largest sample of spectroscopic globular cluster metallicities yet assembled. We compare these metallicities with those derived from Lick indices finding good agreement. In six of the eight galaxies with sufficient numbers of high-quality spectra we find bimodality in the spectroscopic metallicity distribution. Our results imply that most massive early-type galaxies have bimodal metallicity as well as colour distributions. This bimodality suggests that most massive early-type galaxies experienced two periods of star formation.

  4. Latent fingerprint visualization using a scanning Kelvin probe in conjunction with vacuum metal deposition.

    PubMed

    Dafydd, Hefin; Williams, Geraint; Bleay, Stephen

    2014-01-01

    The application of vacuum metal deposition before scanning Kelvin probe visualization of fingerprints is investigated. The potential contrast between fingerprint ridges and furrows is maximized by the use of silver deposition for non-noble metals and gold-zinc deposition for noble metals. The higher susceptibility of eccrine fingerprints to vacuum metal overdeposition is confirmed. Additionally, fingerprints are best developed individually and by building the metal deposition slowly to protect against overdevelopment and variation in the rate of metal condensation. The progress of the metal deposition can be monitored using the scanning Kelvin probe by reference to the change in potential and continuity of the new potential on the surface. The use of acetic acid solution for the recovery of overVMD-developed samples is shown not to be useful. Applying the metal deposition has the additional prospect of increasing surface conductivity and homogeneity and both can aid fingerprint visualization using the scanning Kelvin probe. © 2013 American Academy of Forensic Sciences.

  5. Crossover from the coffee-ring effect to the uniform deposit caused by irreversible cluster-cluster aggregation.

    PubMed

    Crivoi, A; Zhong, X; Duan, Fei

    2015-09-01

    The coffee-ring effect for particle deposition near the three-phase line after drying a pinned sessile colloidal droplet has been suppressed or attenuated in many recent studies. However, there have been few attempts to simulate the mitigation of the effect in the presence of strong particle-particle attraction forces. We develop a three-dimensional stochastic model to investigate the drying process of a pinned colloidal sessile droplet by considering the sticking between particles, which was observed in the experiments. The Monte Carlo simulation results show that by solely promoting the particle-particle attraction in the model, the final deposit shape is transformed from the coffee ring to the uniform film deposition. This phenomenon is modeled using the colloidal aggregation technique and explained by the "Tetris principle," meaning that unevenly shaped or branched particle clusters rapidly build up a sparse structure spanning throughout the entire domain in the drying process. The influence of the controlled parameters is analyzed as well. The simulation is reflected by the drying patterns of the nanofluid droplets through the surfactant control in the experiments.

  6. Crossover from the coffee-ring effect to the uniform deposit caused by irreversible cluster-cluster aggregation

    NASA Astrophysics Data System (ADS)

    Crivoi, A.; Zhong, X.; Duan, Fei

    2015-09-01

    The coffee-ring effect for particle deposition near the three-phase line after drying a pinned sessile colloidal droplet has been suppressed or attenuated in many recent studies. However, there have been few attempts to simulate the mitigation of the effect in the presence of strong particle-particle attraction forces. We develop a three-dimensional stochastic model to investigate the drying process of a pinned colloidal sessile droplet by considering the sticking between particles, which was observed in the experiments. The Monte Carlo simulation results show that by solely promoting the particle-particle attraction in the model, the final deposit shape is transformed from the coffee ring to the uniform film deposition. This phenomenon is modeled using the colloidal aggregation technique and explained by the "Tetris principle," meaning that unevenly shaped or branched particle clusters rapidly build up a sparse structure spanning throughout the entire domain in the drying process. The influence of the controlled parameters is analyzed as well. The simulation is reflected by the drying patterns of the nanofluid droplets through the surfactant control in the experiments.

  7. Fabrication of nanocables by electrochemical deposition inside metal nanotubes.

    PubMed

    Ku, Jie-Ren; Vidu, Ruxandra; Talroze, Raisa; Stroeve, Pieter

    2004-11-24

    We report a novel route for fabricating Au-Te nanocables. Using nanoporous polycarbonate tract-etching (PCTE) membrane as the template, Au nanotubes were fabricated by electroless Au deposition inside the nanopores of the PCTE membrane. Using the Au nanotube membrane as a second template, Te was deposited on the surfaces of the Au nanotubes by slow electrochemical deposition, taking advantage of underpotential deposition (UPD). The deposition rate was sufficiently slow to radially grow Te nanotubes coaxially within the Au nanotubes to form nanocables.

  8. Silicified egg clusters from a Middle Cambrian Burgess Shale type deposit, Guizhou, south China

    NASA Astrophysics Data System (ADS)

    Lin, Jih-Pai; Scott, Andrew C.; Li, Chia-Wei; Wu, Hung-Jen; Ausich, William I.; Zhao, Yuan-Long; Hwu, Yeu-Kuang

    2006-12-01

    Although knowledge of Cambrian fossil eggs and/or embryos has increased dramatically, embryos were previously unknown in siliciclastic settings of coeval strata. Here we report for the first time egg clusters in a fine-grained siliciclastic matrix from the Middle Cambrian Kaili Formation lagerstätte (513 501 Ma), south China. Some were imaged under synchrotron radiation. These spheroids are preferentially preserved as microcrystalline quartz and interpreted as marine invertebrate fossil eggs based on patterns of spheroid arrangement, shape, and analogues of fossil and modern invertebrate eggs. Embryos with cleavage cells are evident in at least one cluster. Detailed element analyses show that eggs are primarily preserved as solid silica replacement, and there is a calcite layer covering the eggs replacing the original organic layer. Silicification of intact invertebrate egg clusters is reported here as a new mode of preservation associated with a Burgess Shale type deposit.

  9. White Dwarfs in the Metal-Rich Open Cluster NGC 6253

    NASA Astrophysics Data System (ADS)

    Jeffery, E. J.; Campos, F.; Romero, A.; Kepler, S. O.

    2017-03-01

    We have obtained 53 images with the g filter and 19 images with the i filter, each with 600-second exposures of the super metal rich open cluster NGC 6253 with the Gemini-South telescope to create deep images of the cluster to observe the cluster white dwarfs for the first time. We will analyze the white dwarf luminosity function to measure the cluster's white dwarf age, search for any anomalous features (as has been seen in the similarly metal rich cluster NGC 6791), and constrain the initial-final mass relation at high metallicities. We present an update on these observations and our program to study the formation of white dwarfs in super high metallicity environments.

  10. Determination of the Structures of Silicon and Metal Doped Silicon Clusters

    NASA Astrophysics Data System (ADS)

    Lyon, Jonathan T.; Fielicke, Andre; Janssens, Ewald; Lievens, Peter

    2014-06-01

    Strongly bound clusters are often used as convenient models for bulk material. Silicon clusters are particularly interesting due to their importance in the electronics industry. We perform experimental IR multiple photon dissociation spectroscopy in the gas-phase, which makes use of a free electron laser, and compare the results with that predicted by density functional and MP2 theory calculations. Comparison of the vibrational spectra with that predicted by theoretical calculations for several structural isomers for each cluster size leads to accurate structural assignments. Here, we present our results for silicon clusters, and compare the structures with those of select transition metal doped SinM clusters. Of particular interest is the transition from exohedral to endoheral metal doped silicon clusters and how the transition size changes for different metal dopant atoms. Journal of Chemical Physics 2012, 136, 064301 e.g., ChemPhysChem 2014, 15, 328.

  11. Color-magnitude diagrams for six metal-rich, low-latitude globular clusters

    NASA Technical Reports Server (NTRS)

    Armandroff, Taft E.

    1988-01-01

    Colors and magnitudes for stars on CCD frames for six metal-rich, low-latitude, previously unstudied globular clusters and one well-studied, metal-rich cluster (47 Tuc) have been derived and color-magnitude diagrams have been constructed. The photometry for stars in 47 Tuc are in good agreement with previous studies, while the V magnitudes of the horizontal-branch stars in the six program clusters do not agree with estimates based on secondary methods. The distances to these clusters are different from prior estimates. Redding values are derived for each program cluster. The horizontal branches of the program clusters all appear to lie entirely redwards of the red edge of the instability strip, as is normal for their metallicities.

  12. A uniform metal distribution in the intergalactic medium of the Perseus cluster of galaxies.

    PubMed

    Werner, Norbert; Urban, Ondrej; Simionescu, Aurora; Allen, Steven W

    2013-10-31

    Most of the metals (elements heavier than helium) produced by stars in the member galaxies of clusters currently reside within the hot, X-ray-emitting intra-cluster gas. Observations of X-ray line emission from this intergalactic medium have suggested a relatively small cluster-to-cluster scatter outside the cluster centres and enrichment with iron out to large radii, leading to the idea that the metal enrichment occurred early in the history of the Universe. Models with early enrichment predict a uniform metal distribution at large radii in clusters, whereas those with late-time enrichment are expected to introduce significant spatial variations of the metallicity. To discriminate clearly between these competing models, it is essential to test for potential inhomogeneities by measuring the abundances out to large radii along multiple directions in clusters, which has not hitherto been done. Here we report a remarkably uniform iron abundance, as a function of radius and azimuth, that is statistically consistent with a constant value of ZFe = 0.306 ± 0.012 in solar units out to the edge of the nearby Perseus cluster. This homogeneous distribution requires that most of the metal enrichment of the intergalactic medium occurred before the cluster formed, probably more than ten billion years ago, during the period of maximal star formation and black hole activity.

  13. Direct deposition of 10-nm metallic features with the scanning tunneling microscope

    SciTech Connect

    McCord, M.A.; Kern, D.P.; Chang, T.H.P.

    1988-11-01

    In this preliminary study we have used a modified scanning tunneling microscope (STM) to directly deposit metallic features as small as 10 nm by decomposing organometallic gases containing tungsten and gold. Dots as well as lines have been formed. Tungsen deposits analyzed by Auger electron spectroscopy contained 48% tungsten, 40% carbon, and 12% oxygen. A resistivity of 0.01 ..cap omega..cm for the deposits was measured by aligning the STM to a metal contact pattern. This is the first reported combination of STM lithography with conventional lithography. A discussion of several interesting physical and chemical mechanisms involved in the deposition process is also presented.

  14. Study of Flux Ratio of C60 to Ar Cluster Ion for Hard DLC Film deposition

    NASA Astrophysics Data System (ADS)

    Miyauchi, K.; Kitagawa, T.; Toyoda, N.; Kanda, K.; Matsui, S.; Yamada, I.

    2003-08-01

    To study the influence of the flux ratio of C60 molecule to Ar cluster ion on DLC film characteristics, DLC films deposited under various flux ratios were characterized with Raman spectrometry and Near Edge X-ray Absorption Fine Structure (NEXAFS). From results of these measurements, hard DLC films were deposited when the flux ratio of C60 to Ar cluster ion was between 0.7 and 4. Furthermore the DLC film with constant sp2 content was obtained in the range of the ratio from 0.7 to 4, which contents are lower values than that of conventional films such as RF plasma. DLC films deposited under the ratio from 1 to 4 had hardness from 40 to 45GPa. It was shown that DLC films with stable properties of low sp2 content and high hardness were formed even when the fluxes were varied from 1 to 4 during deposition. It was indicated that this process was useful in the view of industrial application.

  15. Composite Hybrid Cluster Built from the Integration of Polyoxometalate and a Metal Halide Cluster: Synthetic Strategy, Structure, and Properties.

    PubMed

    Li, Xin-Xiong; Ma, Xiang; Zheng, Wen-Xu; Qi, Yan-Jie; Zheng, Shou-Tian; Yang, Guo-Yu

    2016-09-06

    A step-by-step synthetic strategy, setting up a bridge between the polyoxometalate (POM) and metal halide cluster (MHC) systems, is demonstrated to construct an unprecedented composite hybrid cluster built up from one high-nuclearity cationic MHC [Cu8I6](2+) and eight Anderson-type anionic POMs [HCrMo6O18(OH)6](2-) cross-linked by a tripodal alcohol derivative.

  16. Supported Dendrimer-Encapsulated Metal Clusters: Toward Heterogenizing Homogeneous Catalysts.

    PubMed

    Ye, Rong; Zhukhovitskiy, Aleksandr V; Deraedt, Christophe V; Toste, F Dean; Somorjai, Gabor A

    2017-08-15

    Recyclable catalysts, especially those that display selective reactivity, are vital for the development of sustainable chemical processes. Among available catalyst platforms, heterogeneous catalysts are particularly well-disposed toward separation from the reaction mixture via filtration methods, which renders them readily recyclable. Furthermore, heterogeneous catalysts offer numerous handles-some without homogeneous analogues-for performance and selectivity optimization. These handles include nanoparticle size, pore profile of porous supports, surface ligands and interface with oxide supports, and flow rate through a solid catalyst bed. Despite these available handles, however, conventional heterogeneous catalysts are themselves often structurally heterogeneous compared to homogeneous catalysts, which complicates efforts to optimize and expand the scope of their reactivity and selectivity. Ongoing efforts in our laboratories are aimed to address the above challenge by heterogenizing homogeneous catalysts, which can be defined as the modification of homogeneous catalysts to render them in a separable (solid) phase from the starting materials and products. Specifically, we grow the small nanoclusters in dendrimers, a class of uniform polymers with the connectivity of fractal trees and generally radial symmetry. Thanks to their dense multivalency, shape persistence, and structural uniformity, dendrimers have proven to be versatile scaffolds for the synthesis and stabilization of small nanoclusters. Then these dendrimer-encapsulated metal clusters (DEMCs) are adsorbed onto mesoporous silica. Through this method, we have achieved selective transformations that had been challenging to accomplish in a heterogeneous setting, e.g., π-bond activation and aldol reactions. Extensive investigation into the catalytic systems under reaction conditions allowed us to correlate the structural features (e.g., oxidation states) of the catalysts and their activity. Moreover, we have

  17. First examples of hybrids based on polyoxometalates, metal halide clusters and organic ligands

    SciTech Connect

    Wang Lamei; Fan Yong; Wang Yan; Xiao Lina; Hu Yangyang; Peng Yu; Wang Tiegang; Gao Zhongmin; Zheng Dafang; Cui Xiaobing; Xu Jiqing

    2012-07-15

    Two new organic-inorganic compounds based on polyoxometalates, metal halide clusters and organic ligands: [BW{sub 12}O{sub 40}]{sub 2}[Cu{sub 2}(Phen){sub 4}Cl](H{sub 2}4, 4 Prime -bpy){sub 4}{center_dot}H{sub 3}O{center_dot}5H{sub 2}O (1) and [HPW{sub 12}O{sub 40}][Cd{sub 2}(Phen){sub 4}Cl{sub 2}](4, 4 Prime -bpy) (2) (Phen=1, 10-phenanthroline, bpy=bipyridine), have been prepared and characterized by IR, UV-vis, XPS, XRD and single crystal X-ray diffraction analyses. Crystal structure analyses reveal that compound 1 is constructed from [BW{sub 12}O{sub 40}]{sup 5-}, metal halide clusters [Cu{sub 2}(Phen){sub 4}Cl]{sup +}and 4, 4 Prime -bpy ligands, while compound 2 is constructed from [PW{sub 12}O{sub 40}]{sup 3-}, metal halide cluster [Cd{sub 2}(Phen){sub 4}Cl{sub 2}]{sup 2+} and 4, 4 Prime -bpy ligands. Compound 1 and compound 2 are not common hybrids based on polyoxometalates and metal halide clusters, they also contain dissociated organic ligands, therefore, compound 1 and 2 are the first examples of hybrids based on polyoxometalates, metal halide clusters and organic ligands. - Graphical Abstract: Two new compounds have been synthesized and characterized. Structure analyses revealed that the two compounds are the first examples of hybrids based on polyoxometalates, metal halide clusters and organic ligands. Highlights: Black-Right-Pointing-Pointer First examples of hybrids based on polyoxometalates, metal halide clusters and organic ligands. Black-Right-Pointing-Pointer Two different kinds of metal halide clusters. Black-Right-Pointing-Pointer Supramolecular structures based on polyoxometalates, metal halide clusters and organic ligands. Black-Right-Pointing-Pointer Hybridization of three different of building blocks.

  18. Superhard composite materials including compounds of carbon and nitrogen deposited on metal and metal nitride carbide and carbonitride

    DOEpatents

    Wong, M.S.; Li, D.; Chung, Y.W.; Sproul, W.D.; Xi Chu; Barnett, S.A.

    1998-03-10

    A composite material having high hardness comprises a carbon nitrogen compound, such as CN{sub x} where x is greater than 0.1 and up to 1.33, deposited on a metal or metal compound selected to promote deposition of substantially crystalline CN{sub x}. The carbon nitrogen compound is deposited on a crystal plane of the metal or metal compound sufficiently lattice-matched with a crystal plane of the carbon nitrogen compound that the carbon nitrogen compound is substantially crystalline. A plurality of layers of the compounds can be formed in alternating sequence to provide a multi-layered, superlattice coating having a coating hardness in the range of 45--55 GPa, which corresponds to the hardness of a BN coating and approaches that of a diamond coating. 10 figs.

  19. Superhard composite materials including compounds of carbon and nitrogen deposited on metal and metal nitride, carbide and carbonitride

    DOEpatents

    Wong, M.S.; Li, D.; Chung, Y.W.; Sproul, W.D.; Chu, X.; Barnett, S.A.

    1998-07-07

    A composite material having high hardness comprises a carbon nitrogen compound, such as CN{sub x} where x is greater than 0.1 and up to 1.33, deposited on a metal or metal compound selected to promote deposition of substantially crystalline CN{sub x}. The carbon nitrogen compound is deposited on a crystal plane of the metal or metal compound sufficiently lattice-matched with a crystal plane of the carbon nitrogen compound that the carbon nitrogen compound is substantially crystalline. A plurality of layers of the compounds can be formed in alternating sequence to provide a multi-layered, superlattice coating having a coating hardness in the range of 45--55 GPa, which corresponds to the hardness of a BN coating and approaches that of a diamond coating. 10 figs.

  20. Superhard composite materials including compounds of carbon and nitrogen deposited on metal and metal nitride, carbide and carbonitride

    DOEpatents

    Wong, Ming-Show; Li, Dong; Chung, Yip-Wah; Sproul, William D.; Chu, Xi; Barnett, Scott A.

    1998-01-01

    A composite material having high hardness comprises a carbon nitrogen compound, such as CN.sub.x where x is greater than 0.1 and up to 1.33, deposited on a metal or metal compound selected to promote deposition of substantially crystalline CN.sub.x. The carbon nitrogen compound is deposited on a crystal plane of the metal or metal compound sufficiently lattice-matched with a crystal plane of the carbon nitrogen compound that the carbon nitrogen compound is substantially crystalline. A plurality of layers of the compounds can be formed in alternating sequence to provide a multi-layered, superlattice coating having a coating hardness in the range of 45-55 GPa, which corresponds to the hardness of a BN coating and approaches that of a diamond coating.

  1. Superhard composite materials including compounds of carbon and nitrogen deposited on metal and metal nitride carbide and carbonitride

    DOEpatents

    Wong, Ming-Show; Li, Dong; Chung, Yin-Wah; Sproul, William D.; Chu, Xi; Barnett, Scott A.

    1998-01-01

    A composite material having high hardness comprises a carbon nitrogen compound, such as CN.sub.x where x is greater than 0.1 and up to 1.33, deposited on a metal or metal compound selected to promote deposition of substantially crystalline CN.sub.x. The carbon nitrogen compound is deposited on a crystal plane of the metal or metal compound sufficiently lattice-matched with a crystal plane of the carbon nitrogen compound that the carbon nitrogen compound is substantially crystalline. A plurality of layers of the compounds can be formed in alternating sequence to provide a multi-layered, superlattice coating having a coating hardness in the range of 45-55 GPa, which corresponds to the hardness of a BN coating and approaches that of a diamond coating.

  2. Tetrahedral Clusters of GaMo 4S 8-Type Compounds: A Metal Bonding Analysis

    NASA Astrophysics Data System (ADS)

    Le Beuze, A.; Loirat, H.; Zerrouki, M. C.; Lissillour, R.

    1995-11-01

    Extended Hückel tight binding calculations have been performed on ligated as well as on ligand-free Mo4 and Mo6 extended frames, in order to analyze the metal-metal bonding within the clusters and particularly the appreciable changes of the metal-metal bond lengths through the M4 tetrahedral units contained in GaM4X8 (M = Mo, Nb, V, Ta; X = S, Se, Te), Mo4S4Y4 (Y = Cl, Br, I). A comparison with the M6 octahedral units of the M Mo6X8 (M = Pb, Ag, La; X = S, Se) series is made. By means of DOS, COOP curves, and overlap populations, results clearly display the strong reorganization of the electronic structure of the bare metal clusters network while the ligand interactions occur, inducing a strong reduction of the strength of the metal-metal bonds. We outline the relationship between the metal-metal bond lengths and various parameters such as the valence electron count (VEC) per cluster and the nature of the ligands. Our results indicate that the two series M4 and M6 differ: M-M bond lengths are unaffected by the VEC in the regular M4 cluster, whereas some M-M bond lengths undergo a significant change when the VEC increases in the distorded M6 clusters. Likewise, it is worthy to note that metal d orbitals have a more significant effect in M4 cluster series. In contrast, the metal-ligand covalency induces similar elongations of metal-metal bonds in the two series.

  3. Carbon nanotube-metal cluster composites: a new road to chemical sensors?

    PubMed

    Zhao, Q; Buongiorno Nardelli, M; Lu, W; Bernholc, J

    2005-05-01

    Novel carbon nanotube-metal cluster structures are proposed as prototype systems for molecular recognition at the nanoscale. Ab initio calculations show that already the bare nanotube cluster system displays some specificity because the adsorption of ammonia on a carbon nanotube-Al cluster system is easily detected electrically, while diborane adsorption does not provide an electrical signature. Since there are well-established procedures for attaching molecular receptors to metal clusters, these results provide a "proof-of-principle" for the development of novel, high-specificity molecular sensors.

  4. Temporal stability of magic-number metal clusters: beyond the shell closing model.

    PubMed

    Desireddy, Anil; Kumar, Santosh; Guo, Jingshu; Bolan, Michael D; Griffith, Wendell P; Bigioni, Terry P

    2013-03-07

    The anomalous stability of magic-number metal clusters has been associated with closed geometric and electronic shells and the opening of HOMO-LUMO gaps. Despite this enhanced stability, magic-number clusters are known to decay and react in the condensed phase to form other products. Improving our understanding of their decay mechanisms and developing strategies to control or eliminate cluster instability is a priority, to develop a more complete theory of their stability, to avoid studying mixtures of clusters produced by the decay of purified materials, and to enable technology development. Silver clusters are sufficiently reactive to facilitate the study of the ambient temporal stability of magic-number metal clusters and to begin to understand their decay mechanisms. Here, the solution phase stability of a series of silver:glutathione (Ag:SG) clusters was studied as a function of size, pH and chemical environment. Cluster stability was found to be a non-monotonic function of size. Electrophoretic separations showed that the dominant mechanism involved the redistribution of mass toward smaller sizes, where the products were almost exclusively previously known cluster sizes. Optical absorption spectra showed that the smaller clusters evolved toward the two most stable cluster sizes. The net surface charge was found to play an important role in cluster stabilization although charge screening had no effect on stability, contrary to DLVO theory. The decay mechanism was found to involve the loss of Ag(+) ions and silver glutathionates. Clusters could be stabilized by the addition of Ag(+) ions and destabilized by either the addition of glutathione or the removal of Ag(+) ions. Clusters were also found to be most stable in near neutral pH, where they had a net negative surface charge. These results provide new mechanistic insights into the control of post-synthesis stability and chemical decay of magic-number metal clusters, which could be used to develop design

  5. Structure, dynamic and energetic of mixed transition metal clusters. A computational study of mixed clusters of silver and nickel

    NASA Astrophysics Data System (ADS)

    Hewage, J. W.; Rupika, W. L.; Amar, F. G.

    2012-11-01

    Classical molecular dynamics simulation (MD) with Sutton-Chen potential has been used to generate the minimum energy and to study the thermodynamic and dynamic properties of mixed transition metal cluster motifs of Ag n Ni(13- n) for n ≤ 13. Literature results of thirteen particle clusters of neat silver and nickel atoms were first reproduced before the successive replacement of the silver atom by nickel. Calculation was repeated for both silver-centred and nickel-centred clusters. It was found that the nickel-centred clusters were more stable than the silver-centred clusters. Heat capacities and hence the melting points of silver and nickel-centred clusters were determined by using the Histogram method. Species-centric order parameters developed by Hewage and Amar were used to understand the dynamic behaviour in the transition of silver-centred clusters to more stable nickel-centred clusters. This species-centric order parameter calculation further confirmed the stability of nickel-centred clusters over those of silver-centred species.

  6. Inorganic-Organic Coating via Molecular Layer Deposition Enables Long Life Sodium Metal Anode.

    PubMed

    Zhao, Yang; Goncharova, Lyudmila V; Zhang, Qian; Kaghazchi, Payam; Sun, Qian; Lushington, Andrew; Wang, Biqiong; Li, Ruying; Sun, Xueliang

    2017-09-13

    Metallic Na anode is considered as a promising alternative candidate for Na ion batteries (NIBs) and Na metal batteries (NMBs) due to its high specific capacity, and low potential. However, the unstable solid electrolyte interphase layer caused by serious corrosion and reaction in electrolyte will lead to big challenges, including dendrite growth, low Coulombic efficiency and even safety issues. In this paper, we first demonstrate the inorganic-organic coating via advanced molecular layer deposition (alucone) as a protective layer for metallic Na anode. By protecting Na anode with controllable alucone layer, the dendrites and mossy Na formation have been effectively suppressed and the lifetime has been significantly improved. Moreover, the molecular layer deposition alucone coating shows better performances than the atomic layer deposition Al2O3 coating. The novel design of molecular layer deposition protected Na metal anode may bring in new opportunities to the realization of the next-generation high energy-density NIBs and NMBs.

  7. Depositing aluminum as sacrificial metal to reduce metal-graphene contact resistance

    NASA Astrophysics Data System (ADS)

    Da-cheng, Mao; Zhi, Jin; Shao-qing, Wang; Da-yong, Zhang; Jing-yuan, Shi; Song-ang, Peng; Xuan-yun, Wang

    2016-07-01

    Reducing the contact resistance without degrading the mobility property is crucial to achieve high-performance graphene field effect transistors. Also, the idea of modifying the graphene surface by etching away the deposited metal provides a new angle to achieve this goal. We exploit this idea by providing a new process method which reduces the contact resistance from 597 Ω·μm to sub 200 Ω·μm while no degradation of mobility is observed in the devices. This simple process method avoids the drawbacks of uncontrollability, ineffectiveness, and trade-off with mobility which often exist in the previously proposed methods. Project by the National Science and Technology Major Project, China (Grant No. 2011ZX02707.3), the National Natural Science Foundation of China (Grant No. 61136005), the Chinese Academy of Sciences (Grant No. KGZD-EW-303), and the Project of Beijing Municipal Science and Technology Commission, China (Grant No. Z151100003515003).

  8. Characteristics of epitaxial garnets grown by CVD using single metal alloy sources. [Chemical Vapor Deposition

    NASA Technical Reports Server (NTRS)

    Besser, P. J.; Hamilton, T. N.; Mee, J. E.; Stermer, R. L.

    1974-01-01

    Single metal alloys have been explored as the cation source in the chemical vapor deposition (CVD) of iron garnets. Growth of good quality single crystal garnet films containing as many as five different cations has been achieved over a wide range of deposition conditions. The relationship of film composition to alloy compositions and deposition conditions has been determined for several materials. By proper choice of the alloy composition and the deposition conditions, uncrazed deposits were grown on (111) gadolinium gallium garnet (GGG) substrates. Data on physical, magnetic and optical properties of representative films is presented and discussed.

  9. Characteristics of epitaxial garnets grown by CVD using single metal alloy sources. [Chemical Vapor Deposition

    NASA Technical Reports Server (NTRS)

    Besser, P. J.; Hamilton, T. N.; Mee, J. E.; Stermer, R. L.

    1974-01-01

    Single metal alloys have been explored as the cation source in the chemical vapor deposition (CVD) of iron garnets. Growth of good quality single crystal garnet films containing as many as five different cations has been achieved over a wide range of deposition conditions. The relationship of film composition to alloy compositions and deposition conditions has been determined for several materials. By proper choice of the alloy composition and the deposition conditions, uncrazed deposits were grown on (111) gadolinium gallium garnet (GGG) substrates. Data on physical, magnetic and optical properties of representative films is presented and discussed.

  10. LITHIUM ABUNDANCES OF THE SUPER-METAL-RICH OPEN CLUSTER NGC 6253

    SciTech Connect

    Cummings, Jeffrey D.; Deliyannis, Constantine P.; Maderak, Ryan M.; Anthony-Twarog, Barbara; Twarog, Bruce E-mail: con@astro.indiana.edu E-mail: bjat@ku.edu

    2012-11-01

    High-resolution CTIO 4 m/HYDRA spectroscopy of the super-metal-rich open cluster NGC 6253 ([Fe/H] = +0.43 {+-} 0.01) has been used to study the stellar lithium (Li) abundances near the cluster's turnoff. NGC 6253 greatly expands the range of [Fe/H] for clusters that have a Li abundance analysis. This is important for studying the complicated effects of, and potential correlations with, stellar Fe abundance on surface Li abundance. Comparisons to the younger and less-metal-rich Hyades and to the similarly aged but solar-metallicity M67 show that NGC 6253's Li abundances are qualitatively consistent with the prediction, from Standard Stellar Evolution Theory, that higher-metallicity stars have a greater Li depletion. Comparison with M67 provides evidence that the more-metal-rich NGC 6253 had a higher initial Li, which is consistent with expectations from models of Galactic Li production. NGC 6253 is also compared to the intermediate-aged NGC 3680, NGC 752, and IC 4651 open clusters. Comparison of the Li-gap positions in all six clusters shows that (1) the gap's position in T{sub eff} is independent of metallicity, but (2) higher-metallicity clusters have their gaps in higher-mass stars. In addition, the Li gap's position is shown not to evolve with age, which provides an important constraint for the non-standard depletion mechanisms that may create the Li gap.

  11. Self-Assembly of Silver Metal Clusters of Small Atomicity on Cyclic Peptide Nanotubes.

    PubMed

    Cuerva, Miguel; García-Fandiño, Rebeca; Vázquez-Vázquez, Carlos; López-Quintela, M Arturo; Montenegro, Javier; Granja, Juan R

    2015-11-24

    Subnanometric noble metal clusters, composed by only a few atoms, behave like molecular entities and display magnetic, luminescent and catalytic activities. However, noncovalent interactions of molecular metal clusters, lacking of any ligand or surfactant, have not been seen at work. Theoretically attractive and experimentally discernible, van der Waals forces and noncovalent interactions at the metal/organic interfaces will be crucial to understand and develop the next generation of hybrid nanomaterials. Here, we present experimental and theoretical evidence of noncovalent interactions between subnanometric metal (0) silver clusters and aromatic rings and their application in the preparation of 1D self-assembled hybrid architectures with ditopic peptide nanotubes. Atomic force microscopy, fluorescence experiments, circular dichroism and computational simulations verified the occurrence of these interactions in the clean and mild formation of a novel peptide nanotube and metal cluster hybrid material. The findings reported here confirmed the sensitivity of silver metal clusters of small atomicity toward noncovalent interactions, a concept that could find multiple applications in nanotechnology. We conclude that induced supramolecular forces are optimal candidates for the precise spatial positioning and properties modulation of molecular metal clusters. The reported results herein outline and generalize the possibilities that noncovalent interactions will have in this emerging field.

  12. Reactions of metal cluster anions with inorganic and organic molecules in the gas phase.

    PubMed

    Zhao, Yan-Xia; Liu, Qing-Yu; Zhang, Mei-Qi; He, Sheng-Gui

    2016-07-28

    The study of gas phase ion-molecule reactions by state-of-the-art mass spectrometric experiments in conjunction with quantum chemistry calculations offers an opportunity to clarify the elementary steps and mechanistic details of bond activation and conversion processes. In the past few decades, a considerable number of publications have been devoted to the ion-molecule reactions of metal clusters, the experimentally and theoretically tractable models for the active phase of condensed phase systems. The focus of this perspective concerns progress on activation and transformation of important inorganic and organic molecules by negatively charged metal clusters. The metal cluster anions cover bare metal clusters as well as ligated systems with oxygen, carbon, and nitrogen, among others. The following important issues have been summarized and discussed: (i) dependence of chemical reactivity and selectivity on cluster structures and sizes, metals and metal oxidation states, odd-even electron numbers, etc. and (ii) effects of doping, ligation, and pre-adsorption on the reactivity of metal clusters toward rather inert molecules.

  13. Sub-nanometre sized metal clusters: from synthetic challenges to the unique property discoveries.

    PubMed

    Lu, Yizhong; Chen, Wei

    2012-05-07

    Sub-nanometre sized metal clusters, with dimensions between metal atoms and nanoparticles, have attracted more and more attention due to their unique electronic structures and the subsequent unusual physical and chemical properties. However, the tiny size of the metal clusters brings the difficulty of their synthesis compared to the easier preparation of large nanoparticles. Up to now various synthetic techniques and routes have been successfully applied to the preparation of sub-nanometre clusters. Among the metals, gold clusters, especially the alkanethiolate monolayer protected clusters (MPCs), have been extensively investigated during the past decades. In recent years, silver and copper nanoclusters have also attracted enormous interest mainly due to their excellent photoluminescent properties. Meanwhile, more structural characteristics, particular optical, catalytic, electronic and magnetic properties and the related technical applications of the metal nanoclusters have been discovered in recent years. In this critical review, recent advances in sub-nanometre sized metal clusters (Au, Ag, Cu, etc.) including the synthetic techniques, structural characterizations, novel physical, chemical and optical properties and their potential applications are discussed in detail. We finally give a brief outlook on the future development of metal nanoclusters from the viewpoint of controlled synthesis and their potential applications.

  14. Process for preparation of a seed layer for selective metal deposition

    DOEpatents

    Bernhardt, Anthony F.

    1992-01-01

    Disclosed is a process for selective metal deposition comprising of the steps of: a. formation of an initial surface on a substrate, said initial surface being comprised of at least two layers of which the uppermost is inert, b. exposing the surface to a source of heat in pre-determined places wherein surface activation is desired, and c. deposition of metal on activated portions of said surface.

  15. An investigation of the internal temperature dependence of Pd-Pt cluster beam deposition: A molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Chen, Cha'o.-Kuang; Chang, Shing-Cheng

    2010-02-01

    We investigated the internal temperature dependence of the Pd 1- aPt a cluster beam deposition in the present study via the molecular dynamics simulations of soft-landing. By analysis of the velocity distribution and diffusion coefficient of the bimetallic cluster, Pd atoms with better mobility improved the diffusibility of Pt atoms. The radial composition distribution showed that a Pt-core/Pd-shell structure of the cluster formed at high internal temperatures through migrations of the Pd atoms from inner to surface shells. In the soft-landing process, the diffusing and epitaxial behaviors of the deposited clusters mainly depended on the internal temperature because the incident energy of the cluster was very small. By depositing clusters at high internal temperatures, we obtained a thin film of good epitaxial growth as the energetic cluster impact. Furthermore, nonepitaxial configurations such as scattered nonepitaxial atoms, misoriented particles, and grain boundaries of (1 1 1) planes were produced in the growth of the cluster-assembled film. As the size of the incident cluster increased, the internal temperature of the cluster needed for better interfacial diffusion and contact epitaxy on the substrate also rose.

  16. Polymer-assisted metal deposition (PAMD): a full-solution strategy for flexible, stretchable, compressible, and wearable metal conductors.

    PubMed

    Yu, You; Yan, Casey; Zheng, Zijian

    2014-08-20

    Metal interconnects, contacts, and electrodes are indispensable elements for most applications of flexible, stretchable, and wearable electronics. Current fabrication methods for these metal conductors are mainly based on conventional microfabrication procedures that have been migrated from Si semiconductor industries, which face significant challenges for organic-based compliant substrates. This Research News highlights a recently developed full-solution processing strategy, polymer-assisted metal deposition (PAMD), which is particularly suitable for the roll-to-roll, low-cost fabrication of high-performance compliant metal conductors (Cu, Ni, Ag, and Au) on a wide variety of organic substrates including plastics, elastomers, papers, and textiles. This paper presents i) the principles of PAMD, and how to use it for making ii) flexible, stretchable, and wearable conductive metal electrodes, iii) patterned metal interconnects, and d) 3D stretchable and compressible metal sponges. A critical perspective on this emerging strategy is also provided.

  17. Bright Stars and Metallicity Spread in the Globular Cluster omega Centauri

    NASA Astrophysics Data System (ADS)

    Ortolani, Sergio; Covino, Stefano; Carraro, Giovanni

    The globular cluster omega Centauri (NGC~5139) is the most massive and brightest cluster in our Galaxy. It has also a moderately high mass to light ratio (3.6) and an anomalous flattening (0.83) for a globular cluster. This cluster is also very interesting because it is one of a few examples of globular clusters with a measurable spread in the metal abundance (see Da Costa & Willumsen 1981, Norris et al. 1996, and Suntzeff and Kraft 1996 and references therein) and then it offers a unique, big sample of nearby stars having all the same distance and reddening but showing different metallicity (and age ?) effects. A recent paper by Norris et al. (1997) shows also an interesting correlation between kinematics and metal abundance.

  18. VizieR Online Data Catalog: Metallicity estimates of M31 globular clusters (Galleti+, 2009)

    NASA Astrophysics Data System (ADS)

    Galleti, S.; Bellazzini, M.; Buzzoni, A.; Federici, L.; Fusi Pecci, F.

    2010-04-01

    New empirical relations of [Fe/H] as a function of [MgFe] and Mg2 indices are based on the well-studied galactic globular clusters, complemented with theoretical model predictions for -0.2<=[Fe/H]<=+0.5. Lick indices for M31 clusters from various literature sources (225 clusters) and from new observations by our team (71 clusters) have been transformed into the Trager et al. (2000AJ....119.1645T) system, yielding new metallicity estimates for 245 globular clusters of M31. (3 data files).

  19. Theoretical research program to study transition metal trimers and embedded clusters

    NASA Technical Reports Server (NTRS)

    Walch, S. P.

    1984-01-01

    Small transition metal clusters were studied at a high level of approximation, including all the valence electrons in the calculation and extensive electron correlation, in order to understand the electronic structure of these small metal clusters. By comparison of dimers, trimers, and possibly higher clusters, the information obtained was used to provide insights into the electronic structure of bulk transition metals. Small metal clusters are currently of considerable experimental interest and some information is becomming available both from matrix electron spin resonance studies and from gas phase spectroscopy. Collaboration between theorists and experimentalists is thus expected to be especially profitable at this time since there is some experimental information which can serve to guide the theoretical work.

  20. Theoretical research program to study transition metal trimers and embedded clusters

    NASA Technical Reports Server (NTRS)

    Walch, Stephen P.

    1987-01-01

    The results of ab-initio calculations are reported for (1) small transition metal clusters and (2) potential energy surfaces for chemical reactions important in hydrogen combustion and high temperature air chemistry.

  1. Hard X-ray-induced optical luminescence via biomolecule-directed metal clusters.

    PubMed

    Osakada, Yasuko; Pratx, Guillem; Sun, Conroy; Sakamoto, Masanori; Ahmad, Moiz; Volotskova, Olga; Ong, Qunxiang; Teranishi, Toshiharu; Harada, Yoshie; Xing, Lei; Cui, Bianxiao

    2014-04-07

    Here, we demonstrate that biomolecule-directed metal clusters are applicable in the study of hard X-ray excited optical luminescence, promising a new direction in the development of novel X-ray-activated imaging probes.

  2. Nanostructured europium oxide thin films deposited by pulsed laser ablation of a metallic target in a He buffer atmosphere

    SciTech Connect

    Luna, H.; Franceschini, D. F.; Prioli, R.; Guimaraes, R. B.; Sanchez, C. M.; Canal, G. P.; Barbosa, M. D. L.; Galvao, R. M. O.

    2010-09-15

    Nanostrucured europium oxide and hydroxide films were obtained by pulsed Nd:YAG (532 nm) laser ablation of a europium metallic target, in the presence of a 1 mbar helium buffer atmosphere. Both the produced film and the ambient plasma were characterized. The plasma was monitored by an electrostatic probe, for plume expansion in vacuum or in the presence of the buffer atmosphere. The time evolution of the ion saturation current was obtained for several probe to substrate distances. The results show the splitting of the plume into two velocity groups, being the lower velocity profile associated with metal cluster formation within the plume. The films were obtained in the presence of helium atmosphere, for several target-to-substrate distances. They were analyzed by Rutherford backscattering spectrometry, x-ray diffraction, and atomic force microscopy, for as-deposited and 600 deg. C treated-in-air samples. The results show that the as-deposited samples are amorphous and have chemical composition compatible with europium hydroxide. The thermally treated samples show x-ray diffraction peaks of Eu{sub 2}O{sub 3}, with chemical composition showing excess oxygen. Film nanostructuring was shown to be strongly correlated with cluster formation, as shown by velocity splitting in probe current versus time plots.

  3. Processing of metal and oxygen from lunar deposits

    NASA Technical Reports Server (NTRS)

    Acton, Constance F.

    1992-01-01

    On the moon, some whole rocks may be ores for abundant elements, such as oxygen, but beneficiation will be important if metallic elements are sought from raw lunar dirt. In the extraction process, a beneficiated metallic ore, such as an oxide, sulfide, carbonate, or silicate mineral, is converted to reduced metal. A variety of plausible processing technologies, which includes recovery of meteoritic iron, and processing of lunar ilmenite, are described in this report.

  4. Vacuum deposited polymer/metal films for optical applications

    NASA Astrophysics Data System (ADS)

    Affinito, J. D.; Martin, P. M.; Gross, M. E.; Coronado, C.; Greenwell, E.

    1995-04-01

    Vacuum deposited Polymer/Silver/Polymer reflectors and Tantalum/Polymer/Aluminum Fabry-Perot interference filters were fabricated in a vacuun web coating operation on polyester substrates with a new, high speed deposition process. Reflectivities were measured in the wavelength range from 0.3 to 0.8(mu)m. This new vacuum processing technique has been shown to be capable of deposition line speeds in excess of 500 linear meters/minute. Central to this technique is a new position process for the high rate deposition of polymer films. This polymer process involves the flash evaporation of an acrylic monomer onto a moving substrate. The monomer is subsequently cured by an electron beam or ultraviolet light. This high speed polymer film deposition process has been named the PML process -- for Polymer Multi-Layer. Also, vacuum deposited, index matched, polymer/CaF(sub 2) composites were fabricated from monomer slurries that were subsequently cured with LTV light. This second technique is called the Liquid Multi-Layer (or LML) process. Each of these polymer processes is compatible with each other and with conventional vacuum deposition processes such as sputtering or evaporation.

  5. Far-infrared spectrum of lithium deposited on a gold electrode: Interpretation with use of a cluster model

    SciTech Connect

    Severson, M.W.; Schmidt, P.P.; Pons, S.; Li, J.; Smith, J.J.

    1988-01-15

    A cluster model for the calculation of surface atom vibrations is described. The model assumes central forces between all the atoms of the cluster. With use of a Morse function for the potential energy, the model is used to interpret the recently reported far-infrared spectrum of lithium deposited on a gold electrode.

  6. 25. Steenbock symposium -- Biosynthesis and function of metal clusters for enzymes: Proceedings

    SciTech Connect

    1997-12-31

    This symposium was held June 10--14, 1997 in Madison, Wisconsin. The purpose of this conference was to provide a multidisciplinary forum for exchange of state-of-the-art information on biochemistry of enzymes that have an affinity for metal clusters. Attention is focused on the following: metal clusters involved in energy conservation and remediation; tungsten, molybdenum, and cobalt-containing enzymes; Fe proteins, and Mo-binding proteins; nickel enzymes; and nitrogenase.

  7. Modeling electrochemical deposition inside nanotubes to obtain metal-semiconductor multiscale nanocables or conical nanopores.

    PubMed

    Lebedev, Konstantin; Mafé, Salvador; Stroeve, Pieter

    2005-08-04

    Nanocables with a radial metal-semiconductor heterostructure have recently been prepared by electrochemical deposition inside metal nanotubes. First, a bare nanoporous polycarbonate track-etched membrane is coated uniformly with a metal film by electroless deposition. The film forms a working electrode for further deposition of a semiconductor layer that grows radially inside the nanopore when the deposition rate is slow. We propose a new physical model for the nanocable synthesis and study the effects of the deposited species concentration, potential-dependent reaction rate, and nanopore dimensions on the electrochemical deposition. The problem involves both axial diffusion through the nanopore and radial transport to the nanopore surface, with a surface reaction rate that depends on the axial position and the time. This is so because the radial potential drop across the deposited semiconductor layer changes with the layer thickness through the nanopore. Since axially uniform nanocables are needed for most applications, we consider the relative role of reaction and axial diffusion rates on the deposition process. However, in those cases where partial, empty-core deposition should be desirable (e.g., for producing conical nanopores to be used in single nanoparticle detection), we give conditions where asymmetric geometries can be experimentally realized.

  8. 24 electron cluster formulas as the 'molecular' units of ideal metallic glasses

    NASA Astrophysics Data System (ADS)

    Luo, L. J.; Chen, H.; Wang, Y. M.; Qiang, J. B.; Wang, Q.; Dong, C.; Häussler, P.

    2014-08-01

    It is known that ideal metallic glasses fully complying with the Hume-Rothery stabilization mechanism can be expressed by a universal cluster formula of the form [cluster](glue atom)1 or 3. In the present work, it is shown, after a re-examination of the cluster-resonance model, that the number of electrons per unit cluster formula, e/u, is universally 24. The cluster formulas are then the atomic as well as the electronic structural units, mimicking the 'molecular' formulas for chemical substances. The origin of different electron number per atom ratios e/a is related to the total number of atoms Z in unit cluster formula, e/a = 24/Z. The 24 electron formulas are well confirmed in typical binary and ternary bulk metallic glasses.

  9. Chemical abundances in Virgo cluster spirals - what drives the environmental dependence of galaxy metallicity?

    NASA Astrophysics Data System (ADS)

    Ellison, Sara; Skillman, Evan; Chung, Aeree

    2009-08-01

    The Virgo cluster is not only our nearest massive cluster, but its dynamical infancy also renders it an ideal laboratory for studies of cluster formation and galaxy evolution. Given the intense interest in Virgo, it is astounding that only 9 out of over 100 spirals in its firmament have chemical abundance measurements. We propose to simultaneously address this gap in our fundamental knowledge of Virgo cluster spirals and investigate how the metallicity and abundance gradients of star forming galaxies are sensitive to environment. Our sample consists of 13 Virgo cluster spiral galaxies, preferentially gas-poor early types, which complement the existing metallicity measurements. We also sample a range of clustercentric distances (0.3 -- 3 Mpc from M87), local densities and include several galaxies which exhibit evidence for interactions with the intra-cluster medium.

  10. Chemical vapor deposition of ceramic coatings on metals and ceramic fibers

    NASA Astrophysics Data System (ADS)

    Nable, Jun Co

    2005-07-01

    The research presented in this study consists of two major parts. The first part is about the development of ceramic coatings on metals by chemical vapor deposition (CVD) and metal-organic chemical vapor deposition (MOCVD). Ceramics such as Al2O3 and Cr2O3, are used as protective coatings for materials used at elevated temperatures (>700°C). These metal oxides either exhibit oxidation resistance or have been used as environmental bond coats. Conventional methods of coating by chemical vapor deposition requires deposition temperatures of >950°C which could damage the substrate material during the coating process. Lower deposition temperatures (400 to 600°C) by MOCVD of these metal oxides were successful on Ni metal substrates. Surface modification such as pre-oxidation and etching were also investigated. In addition, a novel approach for the CVD of TiN on metals was developed. This new approach utilizes ambient pressure conditions which lead to deposition temperatures of 800°C or lower compared to conventional CVD of TiN at 1000°C. Titanium nitride can be used as an abrasive and wear coating on cutting and grinding tools. This nitride can also serve as a diffusion coating in metals. The second major part of this research involves the synthesis of interfacial coatings on ceramic reinforcing fibers for ceramic matrix composites. Aluminum and chromium oxides were deposited onto SiC, and Al2O3-SiO 2 fibers by MOCVD. The effects of the interface coatings on the tensile strength of ceramic fibers are also discussed. New duplex interface coatings consisting of BN or TiN together with Al2O3 or ZrO 2 were also successfully deposited and evaluated on SiC fibers.

  11. Sulfide ions as modulators of metal-thiolate cluster size in a plant metallothionein.

    PubMed

    Huber, Tamara; Freisinger, Eva

    2013-06-28

    Metallothioneins are small cysteine-rich proteins coordinating various transition metal ions preferably with the electron configuration d(10). They are ubiquitously present in all phyla, and next to phytochelatins they represent a successful molecular concept for high-capacity metal ion binding. Recent studies showed the incorporation of sulfide ions into the metal-thiolate cluster of metallothionein 2 from the plant Cicer arietinum (cicMT2) increasing the cadmium binding capacity and stability of the cluster. In the present work, the sulfide-induced structural changes accompanying the cluster formation and the sulfide-modulated increase in cluster size are analyzed in detail with a variety of analytical and spectroscopic techniques. Evaluation of the mechanism of sulfide containing Cd(II)-thiolate cluster formation in cicMT2 reveals a strong dependence on the sequence of metal and sulfide additions for successful sulfide incorporation. To probe the general ability of metallothioneins to form sulfide containing larger metal-thiolate clusters, analogous experiments were performed with a mammalian metallothionein. The observation that the cadmium binding ability of rabbit liver MT2A was only slightly increased led to the development of a hypothesis in which the long cysteine-free linker regions present in certain plant metallothioneins may contribute to the accommodation of the respective larger cluster assemblies.

  12. Influence of substrate metal alloy type on the properties of hydroxyapatite coatings deposited using a novel ambient temperature deposition technique.

    PubMed

    Barry, J N; Cowley, A; McNally, P J; Dowling, D P

    2014-03-01

    Hydroxyapatite (HA) coatings are applied widely to enhance the level of osteointegration onto orthopedic implants. Atmospheric plasma spray (APS) is typically used for the deposition of these coatings; however, HA crystalline changes regularly occur during this high-thermal process. This article reports on the evaluation of a novel low-temperature (<47°C) HA deposition technique, called CoBlast, for the application of crystalline HA coatings. To-date, reports on the CoBlast technique have been limited to titanium alloy substrates. This study addresses the suitability of the CoBlast technique for the deposition of HA coatings on a number of alternative metal alloys utilized in the fabrication of orthopedic devices. In addition to titanium grade 5, both cobalt chromium and stainless steel 316 were investigated. In this study, HA coatings were deposited using both the CoBlast and the plasma sprayed techniques, and the resultant HA coating and substrate properties were evaluated and compared. The CoBlast-deposited HA coatings were found to present similar surface morphologies, interfacial properties, and composition irrespective of the substrate alloy type. Coating thickness however displayed some variation with the substrate alloy, ranging from 2.0 to 3.0 μm. This perhaps is associated with the electronegativity of the metal alloys. The APS-treated samples exhibited evidence of both coating, and significantly, substrate phase alterations for two metal alloys; titanium grade 5 and cobalt chrome. Conversely, the CoBlast-processed samples exhibited no phase changes in the substrates after depositions. The APS alterations were attributed to the brief, but high-intensity temperatures experienced during processing.

  13. Growth and optical properties of Ag clusters deposited on poly(ethylene terephthalate).

    PubMed

    Flores-Camacho, J M; Weidlinger, G; Sun, L D; Schmidegg, K; Hohage, M; Primetzhofer, D; Bauer, P; Zeppenfeld, P

    2011-07-08

    The growth and concomitant evolution of the optical properties of Ag nano-clusters deposited on biaxially extruded poly(ethylene terephthalate) films is studied by reflectance difference spectroscopy. It is demonstrated by low energy ion scattering and simulated optical spectra that the clusters form a two-dimensional layer buried beneath the surface of the substrate. The experimental spectra are described by simulations in which different configurations of the host such as anisotropy, amorphization, and dilution are considered in an effective medium approach. The contribution of the anisotropic substrate is used to explain the resulting line shapes. We also discuss the role of the rate of change of the filling fraction with Ag coverage in the evolution of the spectra and the detection of the onset of coalescence by optical means.

  14. Growth and optical properties of Ag clusters deposited on poly(ethylene terephthalate)

    NASA Astrophysics Data System (ADS)

    Flores-Camacho, J. M.; Weidlinger, G.; Sun, L. D.; Schmidegg, K.; Hohage, M.; Primetzhofer, D.; Bauer, P.; Zeppenfeld, P.

    2011-07-01

    The growth and concomitant evolution of the optical properties of Ag nano-clusters deposited on biaxially extruded poly(ethylene terephthalate) films is studied by reflectance difference spectroscopy. It is demonstrated by low energy ion scattering and simulated optical spectra that the clusters form a two-dimensional layer buried beneath the surface of the substrate. The experimental spectra are described by simulations in which different configurations of the host such as anisotropy, amorphization, and dilution are considered in an effective medium approach. The contribution of the anisotropic substrate is used to explain the resulting line shapes. We also discuss the role of the rate of change of the filling fraction with Ag coverage in the evolution of the spectra and the detection of the onset of coalescence by optical means.

  15. Effect of functionalization of boron nitride flakes by main group metal clusters on their optoelectronic properties

    NASA Astrophysics Data System (ADS)

    Chakraborty, Debdutta; Chattaraj, Pratim Kumar

    2017-10-01

    The possibility of functionalizing boron nitride flakes (BNFs) with some selected main group metal clusters, viz. OLi4, NLi5, CLi6, BLI7 and Al12Be, has been analyzed with the aid of density functional theory (DFT) based computations. Thermochemical as well as energetic considerations suggest that all the metal clusters interact with the BNF moiety in a favorable fashion. As a result of functionalization, the static (first) hyperpolarizability (β ) values of the metal cluster supported BNF moieties increase quite significantly as compared to that in the case of pristine BNF. Time dependent DFT analysis reveals that the metal clusters can lower the transition energies associated with the dominant electronic transitions quite significantly thereby enabling the metal cluster supported BNF moieties to exhibit significant non-linear optical activity. Moreover, the studied systems demonstrate broad band absorption capability spanning the UV–visible as well as infra-red domains. Energy decomposition analysis reveals that the electrostatic interactions principally stabilize the metal cluster supported BNF moieties.

  16. Mixed protein-templated luminescent metal clusters (Au and Pt) for H2O2 sensing

    NASA Astrophysics Data System (ADS)

    Li, Min; Yang, Da-Peng; Wang, Xiansong; Lu, Jianxin; Cui, Daxiang

    2013-04-01

    A simple and cost-effective method to synthesize the luminescent noble metal clusters (Au and Pt) in chicken egg white aqueous solution at room temperature is reported. The red-emitting Au cluster is used as fluorescent probe for sensitive detection of H2O2.

  17. Deposition of Cu Nanoparticles on the Surface of Metallic Aluminum

    NASA Astrophysics Data System (ADS)

    Lescinskis, A.; Katkevics, J.; Erts, D.; Viksna, A.

    2012-08-01

    Deposition of Cu particles by electrolysis at constant electrode potential and by internal electrolysis methods was investigated. The composition of deposited material was confirmed by optical and scanning electron microscope methods. Combination of electrolysis at constant electrode potential with internal electrolysis method was found most effective for fabrication of nanoparticle arrays. Single crystalline Cu particles are fabricated by internal electrolysis, while polycrystalline ones obtained by combined chronopotentiometric and internal electrolysis methods. The formation mechanism of Cu nanoparticles is described.

  18. Particle size effect for metal pollution analysis of atmospherically deposited dust

    NASA Astrophysics Data System (ADS)

    Al-Rajhi, M. A.; Al-Shayeb, S. M.; Seaward, M. R. D.; Edwards, H. G. M.

    The metallic compositions of 231 atmospherically deposited dust samples obtained from widely-differing environments in Riyadh city, Saudi Arabia, have been investigated in relation to the particle size distributions. Sample data are presented which show that particle size classification is very important when analysing dust samples for atmospheric metal pollution studies. By cross-correlation and comparison, it was found that the best way to express the results of the metal concentration trend was as an average of particle ratios. Correlations between the six metals studied, namely Pb, Cr, Ni, Cu, Zn and Li, were found for every particle size (eight categories) and reveal that the metal concentrations increased as the particle size decreased. On the basis of this work, it is strongly recommended that future international standards for metal pollutants in atmospherically deposited dusts should be based on particle size fractions.

  19. Clustered streamlined forms in Athabasca Valles, Mars: Evidence for sediment deposition during floodwater ponding

    USGS Publications Warehouse

    Burr, D.

    2005-01-01

    A unique clustering of layered streamlined forms in Athabasca Valles is hypothesized to reflect a significant hydraulic event. The forms, interpreted as sedimentary, are attributed to extensive sediment deposition during ponding and then streamlining of this sediment behind flow obstacles during ponded water outflow. These streamlined forms are analogous to those found in depositional basins and other loci of ponding in terrestrial catastrophic flood landscapes. These terrestrial streamlined forms can provide the best opportunity for reconstructing the history of the terrestrial flooding. Likewise, the streamlined forms in Athabasca Valles may provide the best opportunity to reconstruct the recent geologic history of this young Martian outflow channel. ?? 2005 Elsevier B.V. All rights reserved.

  20. Porphyrins as Templates for Site-Selective Atomic Layer Deposition: Vapor Metalation and in Situ Monitoring of Island Growth

    SciTech Connect

    Avila, Jason R.; Emery, Jonathan D.; Pellin, Michael J.; Martinson, Alex B. F.; Farha, Omar K.; Hupp, Joseph T.

    2016-08-10

    Examinations of enzymatic catalysts suggest one key to efficient catalytic activity is discrete size metallo clusters. Mimicking enzymatic cluster systems is synthetically challenging because conventional solution methods are prone to aggregation or require capping of the cluster, thereby limiting its catalytic activity. We introduce site-selective atomic layer deposition (ALD) on porphyrins as an alternative approach to grow isolated metal oxide islands that are spatially separated. Surface-bound tetra-acid free base porphyrins (H2TCPP) may be metalated with Mn using conventional ALD precursor exposure to induce homogeneous hydroxide synthetic handles which acts as a nucleation point for subsequent ALD MnO island growth. Analytical fitting of in situ QCM mass uptake reveals island growth to be hemispherical with a convergence radius of 1.74 nm. This growth mode is confirmed with synchrotron grazing-incidence small-angle X-ray scattering (GISAXS) measurements. Finally, we extend this approach to other ALD chemistries to demonstrate the generality of this route to discrete metallo island materials.

  1. Infrared Probes of Metal Cluster Structure and Bonding

    DTIC Science & Technology

    2006-03-01

    corresponding niobium and tantalum analogues of these clusters. Preliminary attempts were conducted for the production of other ligand- coated ...interactions. Prospects are evaluated for macroscopic synthesis of cluster materials and synthesis experiments employing ligand- coating strategies have been...experiments that isolate ligand- coated nanoclusters in solution were conducted using a new laser ablation flowtube reactor. Graduate and undergraduate

  2. The relationship between hydrocarbon and stratabound metal sulfide deposits: The Upper Smackover as an analog

    SciTech Connect

    Denham, M.E. )

    1991-03-01

    A genetic link between hydrocarbon and stratabound metal sulfide deposits has often been suggested. Both are thought to result from similar processes operating during the evolution of sedimentary basins, yet exploitable hydrocarbon and metal sulfide deposits are not found together. Consequently, the nature of their genetic relationship remains unclear. The Upper Jurassic Smackover Formation of the North Louisiana Salt Basin - a prolific hydrocarbon producer - contains disseminated authigenic sulfide minerals reminiscent of stratabound metal sulfide deposits. The close association of these sulfide minerals with hydrocarbon deposits provides an opportunity to examine the relation between the two. The mineralogy and chemistry of late-stage authigenic phases in the Upper Smackover are similar to ore and 'gangue' minerals of Mississippi Valley-type sulfide deposits. The sulfide minerals consist of replacement or pore-filling sphalerite, galena, pyrite, marcasite, and chalcopyrite. The mineralogy and chemistry of the sulfides and their related minerals vary spatially throughout the basin. These variations reflect local processes and the sources of the sulfide minerals' constituents. The same source rocks from which hydrocarbons are derived are likely sources of base metal ions. Likewise, reduced sulfur is related to hydrocarbons by either a common source or by thermochemical sulfate reduction. Thus, spatial variations in chemistry and mineralogy of the late-stage authigenic sulfides of the Upper Smackover may be the key to understanding the relationship between hydrocarbons and stratabound metal sulfide deposits.

  3. Chemical vapor deposition and atomic layer deposition of metal oxide and nitride thin films

    NASA Astrophysics Data System (ADS)

    Barton, Jeffrey Thomas

    Processes for depositing thin films with various electronic, optical, mechanical, and chemical properties are indispensable in many industries today. Of the many deposition methods available, chemical vapor deposition (CVD) has proved over time to be one of the most flexible, efficient, and cost-effective. Atomic layer deposition (ALD) is a newer process that is gaining favor as a method for depositing films with excellent properties and unparalleled precision. This work describes the development of novel CVD and ALD processes to deposit a variety of materials. Hafnium oxide and zirconium oxide show promise as replacements for SiO 2 as gate dielectrics in future-generation transistors. These high-k materials would provide sufficient capacitance with layers thick enough to avoid leakage from tunneling. An ALD method is presented here for depositing conformal hafnium oxide from tetrakis-(diethylamido)hafnium and oxygen gas. A CVD method for depositing zirconium oxide from tetrakis-(dialkylamido)zirconium and either oxygen gas or water vapor is also described. The use of copper for interconnects in integrated circuits requires improved diffusion barrier materials, given its high diffusivity compared to the previously-used aluminum and tungsten. Tungsten nitride has a low resistivity among barrier materials, and can be deposited in amorphous films that are effective diffusion barriers in layers as thin as a few nanometers. Here we demonstrate CVD and plasma-enhanced CVD methods to deposit tungsten nitride films from bis-(dialkylamido)bis-( tert-butylimido)tungsten precursors and ammonia gas. Recent findings had shown uniform copper growth on tantalum silicate films, without the dewetting that usually occurs on oxide surfaces. Tantalum and tungsten silicates were deposited by a CVD reaction from the reaction of either tris-(diethylamido)ethylimido tantalum or bis-(ethylmethylamido)-bis-( tert-butylimido)tungsten with tris-(tert-butoxy)silanol. The ability of evaporated

  4. Percolation of gallium dominates the electrical resistance of focused ion beam deposited metals

    SciTech Connect

    Faraby, H.; DiBattista, M.; Bandaru, P. R.

    2014-04-28

    Metal deposition through focused ion beam (FIB) based systems is thought to result in material composed of the primary metal from the metallo-organic precursor in addition to carbon, oxygen, and gallium. We determined, through electrical resistance and chemical composition measurements on a wide range of FIB deposited platinum and tungsten lines, that the gallium ion (Ga{sup +}) concentration in the metal lines plays the dominant role in controlling the electrical resistivity. Effective medium theory, based on McLachlan's formalisms, was used to describe the relationship between the Ga{sup +} concentration and the corresponding resistivity.

  5. Atomic layer deposition by reaction of molecular oxygen with tetrakisdimethylamido-metal precursors

    SciTech Connect

    Provine, J Schindler, Peter; Torgersen, Jan; Kim, Hyo Jin; Karnthaler, Hans-Peter; Prinz, Fritz B.

    2016-01-15

    Tetrakisdimethylamido (TDMA) based precursors are commonly used to deposit metal oxides such as TiO{sub 2}, ZrO{sub 2}, and HfO{sub 2} by means of chemical vapor deposition and atomic layer deposition (ALD). Both thermal and plasma enhanced ALD (PEALD) have been demonstrated with TDMA-metal precursors. While the reactions of TDMA-type precursors with water and oxygen plasma have been studied in the past, their reactivity with pure O{sub 2} has been overlooked. This paper reports on experimental evaluation of the reaction of molecular oxygen (O{sub 2}) and several metal organic precursors based on TDMA ligands. The effect of O{sub 2} exposure duration and substrate temperature on deposition and film morphology is evaluated and compared to thermal reactions with H{sub 2}O and PEALD with O{sub 2} plasma.

  6. Metal Sulfide Cluster Complexes and their Biogeochemical Importance in the Environment

    NASA Astrophysics Data System (ADS)

    Luther, George W.; Rickard, David T.

    2005-10-01

    Aqueous clusters of FeS, ZnS and CuS constitute a major fraction of the dissolved metal load in anoxic oceanic, sedimentary, freshwater and deep ocean vent environments. Their ubiquity explains how metals are transported in anoxic environmental systems. Thermodynamic and kinetic considerations show that they have high stability in oxic aqueous environments, and are also a significant fraction of the total metal load in oxic river waters. Molecular modeling indicates that the clusters are very similar to the basic structural elements of the first condensed phase forming from aqueous solutions in the Fe-S, Zn-S and Cu-S systems. The structure of the first condensed phase is determined by the structure of the cluster in solution. This provides an alternative explanation of Ostwald's Rule, where the most soluble, metastable phases form before the stable phases. For example, in the case of FeS, we showed that the first condensed phase is nanoparticulate, metastable mackinawite with a particle size of 2 nm consisting of about 150 FeS subunits, representing the end of a continuum between aqueous FeS clusters and condensed material. These metal sulfide clusters and nanoparticles are significant in biogeochemistry. Metal sulfide clusters reduce sulfide and metal toxicity and help drive ecology. FeS cluster formation drives vent ecology and AgS cluster formation detoxifies Ag in Daphnia magna neonates. We also note a new reaction between FeS and DNA and discuss the potential role of FeS clusters in denaturing DNA.

  7. Using electroless deposition for the preparation of micron sized polymer/metal core/shell particles and hollow metal spheres.

    PubMed

    Tierno, Pietro; Goedel, Werner A

    2006-02-23

    Uniform and stable core-shell microspheres composed of a poly(methyl methacrylate) (PMMA) core and a thin metallic shell of nickel-phosphorus, cobalt-phosphorus, or mixed metal alloys (CoNiP, NiFeP, CoFeP) were prepared by dispersion polymerization of methyl methacrylate followed by electroless plating. The presence of the metallic shell around the particles was confirmed by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and photoelectron spectroscopy. Transmission electron microscopy images of the cross-section of individual particles show that the thickness of the metal/alloy can be precisely tuned by adjusting the immersion time of the microspheres in the electroless bath. Depending on the deposited metallic material, various magnetic properties, from paramagnetic to ferromagnetic, are achieved. Finally, uniform hollow metallic spheres composed of nickel, cobalt, or nickel-cobalt alloy are obtained by dissolving the polymer core.

  8. Metal-AlN cermet solar selective coatings deposited by direct current magnetron sputtering technology

    NASA Astrophysics Data System (ADS)

    Zhang, Qi-Chu

    1998-02-01

    A series of metal-aluminium nitride (M-AlN) cermet materials for solar selective coatings was deposited by a novel direct current (d.c.) magnetron sputtering technology. Aluminium nitride was used as the ceramic component in the cermets, and stainless steel (SS), nickel-based alloy 0022-3727/31/4/003/img1 (NiCr), molybdenum-based alloy 0022-3727/31/4/003/img2 (TZM) and tungsten were used as the metallic components. The aluminium nitride ceramic and metallic components of the cermets were deposited by simultaneously running both an aluminium target and another metallic target in a gas mixture of argon and nitrogen. The ceramic component was deposited by d.c. reactive sputtering and the metallic component by d.c. non-reactive sputtering. The total sputtering gas pressure was 0.8-1.0 Pa and the partial pressure of reactive nitrogen gas was set at 0.020-0.025 Pa which is sufficiently high to ensure that a nearly pure AlN ceramic sublayer was deposited by d.c. reactive sputtering. Because of the excellent nitriding resistance of stainless steel and the other alloys and metal, a nearly pure metallic sublayer was deposited by d.c. sputtering at this low nitrogen partial pressure. A multilayered system, consisting of alternating metallic and AlN ceramic sublayers, was deposited by substrate rotation. This multisublayer system can be considered as a macrohomogeneous cermet layer with metal volume fraction determined by controlling the thicknesses of metallic and ceramic sublayers. Following this procedure, M-AlN cermet solar selective coatings with a double cermet layer structure were deposited. The films of these selective surfaces have the following structure: a low metal volume fraction cermet layer is placed on a high metal volume fraction cermet layer which in turn is placed on an aluminium metal infrared reflection layer. The top surface layer consists of an aluminium nitride antireflection layer. A solar absorptance of 0.92-0.96 and a normal emittance of 0.03-0.05 at

  9. One-dimensional fast migration of vacancy clusters in metals

    SciTech Connect

    Matsukawa, Yoshitaka; Zinkle, Steven J

    2007-01-01

    The migration of point defects, e.g. crystal lattice vacancies and self-interstitial atoms (SIAs), typically occurs through three-dimensional (3-D) random walk. However, when vacancies and SIAs agglomerate with like defects forming clusters, the migration mode may change. Recently, atomic-scale computer simulations using molecular dynamics (MD) codes have reported that nanometer-sized two-dimensional (2-D) clusters of SIAs exhibit one-dimensional (1-D) fast migration1-7. The 1-D migration mode transports the entire cluster containing several tens of SIAs with a mobility comparable to single SIAs3. This anisotropic migration of SIA clusters can have a significant impact on the evolution of a material fs neutron-irradiation damage microstructure, which dominates the material fs lifetime in nuclear reactor environments8-9. This is also proposed to be a key physical mechanism for the self-organization of nanometer-sized sessile vacancy cluster arrays10-13. Given these findings for SIA clusters, a fundamental question is whether the 1-D migration mode is also possible for 2-D clusters of vacancies. Preceding MD results predicted that 1-D migration of vacancy clusters is possible in body-centered cubic (bcc) iron, but not in face-centered cubic (fcc) copper2. Previous experimental studies have reported 1-D migration of SIA clusters14, but there have been no observations of 1-D vacancy cluster migration. Here we present the first experimental transmission electron microscopy (TEM) dynamic observation demonstrating the 1-D migration of vacancy clusters in fcc gold. It was found that the mobility of the vacancy clusters via the 1-D migration is much higher than single vacancies via 3-D random walk and comparable to single SIAs via 3-D random walk. Hence, the mobility of the glissile clusters is not associated with the character of their constituent point defects. Dynamic conversion of a planar vacancy loop into a 3-D stacking fault tetrahedron geometry was also observed.

  10. Soluble Nutrient and Trace Metal Fluxes from Aerosol Dry Deposition to Elkhorn Slough, CA

    NASA Astrophysics Data System (ADS)

    Gray, E. T.; Paytan, A.; Haskins, J.

    2009-12-01

    Atmospheric deposition has been widely recognized as a source of pollutants and nutrients to coastal ecosystems. Specifically, deposition includes nitrogen compounds, sulfur compounds, mercury, pesticides, phosphate, trace metals and other toxic compounds that can travel great distances in aerosols. These components can come from both natural (volcanoes, mineral dust, forest fires) and anthropogenic (fossil fuels, chemical byproducts, incineration of waste) sources. These pollutants may affect ecosystem health and water quality with environmental impacts such as eutrophication, contaminated fish and harmful algal blooms. In this study we focus on dry deposition to Elkhorn Slough, California. Size fractionated aerosol samples (PM 2.5 and PM 10) collected continuously over a seven day period using a cascade impactor are used along with a deposition model to determine the soluble nutrient and trace metal fluxes on the Elkhorn Slough ecosystem. Atmospheric deposition inputs will be compared to other sources and their potential impact evaluated.

  11. Near-infrared photometry of globular clusters towards the Galactic bulge: observations and photometric metallicity indicators

    NASA Astrophysics Data System (ADS)

    Cohen, Roger E.; Moni Bidin, Christian; Mauro, Francesco; Bonatto, Charles; Geisler, Douglas

    2017-01-01

    We present wide-field JHKS photometry of 16 Galactic globular clusters located towards the Galactic bulge, calibrated on the Two Micron All-Sky Survey photometric system. Differential reddening corrections and statistical field star decontamination are employed for all of these clusters before fitting fiducial sequences to the cluster red giant branches (RGBs). Observed values and uncertainties are reported for several photometric features, including the magnitude of the RGB bump, tip, the horizontal branch (HB) and the slope of the upper RGB. The latest spectroscopically determined chemical abundances are used to build distance- and reddening-independent relations between observed photometric features and cluster metallicity, optimizing the sample size and metallicity baseline of these relations by supplementing our sample with results from the literature. We find that the magnitude difference between the HB and the RGB bump can be used to predict metallicities, in terms of both iron abundance [Fe/H] and global metallicity [M/H], with a precision of better than 0.1 dex in all three near-IR bandpasses for relatively metal-rich ([M/H] ≳ -1) clusters. Meanwhile, both the slope of the upper RGB and the magnitude difference between the RGB tip and bump are useful metallicity indicators over the entire sampled metallicity range (-2 ≲ [M/H] ≲ 0) with a precision of 0.2 dex or better, despite model predictions that the RGB slope may become unreliable at high (near-solar) metallicities. Our results agree with previous calibrations in light of the relevant uncertainties, and we discuss implications for clusters with controversial metallicities as well as directions for further investigation.

  12. Particle clustering and dielectric enhancement in percolating metal-insulator composites

    NASA Astrophysics Data System (ADS)

    Doyle, William T.

    1995-11-01

    An effective cluster model has been developed [Phys. Rev. B 42, 9319 (1990)] that treats a disordered suspension of monodisperse metal spheres as a mixture of isolated spheres and close-packed spherical clusters of spheres using the Clausius-Mossotti or Maxwell equations. The effective cluster model is adapted to such suspensions with a random intermingled cluster topology using Bruggemann's symmetrical equation. Model susceptibilities for the two cluster topologies are contrasted with one another and compared with experiments. Guillien's permittivity measurements [Ann. Phys. (Paris) Ser. 11 16, 205 (1941)] and Turner's conductivity measurements [Chem. Eng. Sci. 31, 487 (1976)] exemplify nonpercolating island topology suspensions. The permittivity measurements of Grannan, Garland, and Tanner [Phys. Rev. Lett. 46, 375 (1981)] exemplify percolating random topology clusters. The models for both cluster topologies are in excellent agreement with experiment over the entire accessible range of volume loading.

  13. Formation of metal clusters in halloysite clay nanotubes

    DOE PAGES

    Vinokurov, Vladimir A.; Stavitskaya, Anna V.; Chudakov, Yaroslav A.; ...

    2017-02-16

    We developed ceramic core-shell materials based on abundant halloysite clay nanotubes with enhanced heavy metal ions loading through Schiff base binding. These clay tubes are formed by rolling alumosilicate sheets and have diameter of c.50 nm, a lumen of 15 nm and length ~1 μm. This allowed for synthesis of metal nanoparticles at the selected position: (1) on the outer surface seeding 3-5 nm metal particles on the tubes; (2) inside the tube’s central lumen resulting in 10-12 nm diameter metal cores shelled with ceramic wall; and (3) smaller metal nanoparticles intercalated in the tube’s wall allowing up to 9more » wt% of Ru, and Ag loading. These composite materials have high surface area providing a good support for catalytic nanoparticles, and can also be used for sorption of metal ions from aqueous solutions.« less

  14. Formation of metal clusters in halloysite clay nanotubes

    PubMed Central

    Vinokurov, Vladimir A.; Stavitskaya, Anna V.; Chudakov, Yaroslav A.; Ivanov, Evgenii V.; Shrestha, Lok Kumar; Ariga, Katsuhiko; Darrat, Yusuf A.; Lvov, Yuri M.

    2017-01-01

    Abstract We developed ceramic core-shell materials based on abundant halloysite clay nanotubes with enhanced heavy metal ions loading through Schiff base binding. These clay tubes are formed by rolling alumosilicate sheets and have diameter of c.50 nm, a lumen of 15 nm and length ~1 μm. This allowed for synthesis of metal nanoparticles at the selected position: (1) on the outer surface seeding 3–5 nm metal particles on the tubes; (2) inside the tube’s central lumen resulting in 10–12 nm diameter metal cores shelled with ceramic wall; and (3) smaller metal nanoparticles intercalated in the tube’s wall allowing up to 9 wt% of Ru, and Ag loading. These composite materials have high surface area providing a good support for catalytic nanoparticles, and can also be used for sorption of metal ions from aqueous solutions. PMID:28458738

  15. Particulate Trace Metal Composition in the Western Philippine Sea: the importance of anthropogenic aerosol deposition

    NASA Astrophysics Data System (ADS)

    Liao, W. H.; Ho, T. Y.

    2016-02-01

    The Western Philippine Sea (WPS), receiving huge amount of East Asian aerosols in winter and spring, is an ideal platform to investigate the impact of aerosol deposition on trace metal cycling in the oceanic surface water. Particulate trace metal composition provides useful information to elucidate the relative contribution of trace metal sources. In this study, we collected size-fractionated particles in the water column through two different seasons to investigate their trace metal composition and seasonal variability. Our results show that most of trace metal to phosphorus (P) normalized quotas in the size-fractionated particles are one to two orders of magnitude higher than intracellular trace metal quota in phytoplankton. Since all the particles collected are composed of biotic particles, the elevated trace metal to P quotas indicate that extracellular adsorption of trace metal accounts for larger amount than intracellular assimilation. In addition, the metal to Al ratios were similar to the ratios observed in aerosols, indicating that the metals mainly originated from aerosols. Overall, the extracellular adsorption of aerosol metals account for most of the particulate trace metals in the plankton samples. Our results prove the importance of aerosol metals on particulate trace metal composition in the open ocean. The impact of the input of anthropogenic aerosols on marine biogeochemistry deserves further studies in the global open ocean.

  16. Structures and stability of metal-doped GenM (n = 9, 10) clusters

    NASA Astrophysics Data System (ADS)

    Qin, Wei; Lu, Wen-Cai; Xia, Lin-Hua; Zhao, Li-Zhen; Zang, Qing-Jun; Wang, C. Z.; Ho, K. M.

    2015-06-01

    The lowest-energy structures of neutral and cationic GenM (n = 9, 10; M = Si, Li, Mg, Al, Fe, Mn, Pb, Au, Ag, Yb, Pm and Dy) clusters were studied by genetic algorithm (GA) and first-principles calculations. The calculation results show that doping of the metal atoms and Si into Ge9 and Ge10 clusters is energetically favorable. Most of the metal-doped Ge cluster structures can be viewed as adding or substituting metal atom on the surface of the corresponding ground-state Gen clusters. However, the neutral and cationic FeGe9,10,MnGe9,10 and Ge10Al are cage-like with the metal atom encapsulated inside. Such cage-like transition metal doped Gen clusters are shown to have higher adsorption energy and thermal stability. Our calculation results suggest that Ge9,10Fe and Ge9Si would be used as building blocks in cluster-assembled nanomaterials because of their high stabilities.

  17. Mo-Cu metal cluster formation and binding in an orange protein isolated from Desulfovibrio gigas.

    PubMed

    Carepo, Marta S P; Pauleta, Sofia R; Wedd, Anthony G; Moura, José J G; Moura, Isabel

    2014-06-01

    The orange protein (ORP) isolated from the sulfate-reducing bacterium Desulfovibrio gigas (11.8 kDa) contains a mixed-metal sulfide cluster of the type [S2MoS2CuS2MoS2](3-) noncovalently bound to the polypeptide chain. The D. gigas ORP was heterologously produced in Escherichia coli in the apo form. Different strategies were used to reconstitute the metal cluster into apo-ORP and obtain insights into the metal cluster synthesis: (1) incorporation of a synthesized inorganic analogue of the native metal cluster and (2) the in situ synthesis of the metal cluster on the addition to apo-ORP of copper chloride and tetrathiomolybdate or tetrathiotungstate. This latter procedure was successful, and the visible spectrum of the Mo-Cu reconstituted ORP is identical to the one reported for the native protein with absorption maxima at 340 and 480 nm. The (1)H-(15)N heteronuclear single quantum coherence spectra of the reconstituted ORP obtained by strategy 2, in contrast to strategy 1, exhibited large changes, which required sequential assignment in order to identify, by chemical shift differences, the residues affected by the incorporation of the cluster, which is stabilized inside the protein by both electrostatic and hydrophobic interactions.

  18. Structures and stability of metal-doped GenM (n = 9, 10) clusters

    DOE PAGES

    Qin, Wei; Lu, Wen-Cai; Xia, Lin-Hua; ...

    2015-06-26

    The lowest-energy structures of neutral and cationic Ge nM (n = 9, 10; M = Si, Li, Mg, Al, Fe, Mn, Pb, Au, Ag, Yb, Pm and Dy) clusters were studied by genetic algorithm (GA) and first-principles calculations. The calculation results show that doping of the metal atoms and Si into Ge9 and Ge10 clusters is energetically favorable. Most of the metal-doped Ge cluster structures can be viewed as adding or substituting metal atom on the surface of the corresponding ground-state Gen clusters. However, the neutral and cationic FeGe9,10,MnGe9,10 and Ge10Al are cage-like with the metal atom encapsulated inside. Suchmore » cage-like transition metal doped Gen clusters are shown to have higher adsorption energy and thermal stability. Our calculation results suggest that Ge9,10Fe and Ge9Si would be used as building blocks in cluster-assembled nanomaterials because of their high stabilities.« less

  19. Size controlled deposition of Cu and Si nano-clusters by an ultra-high vacuum sputtering gas aggregation technique

    NASA Astrophysics Data System (ADS)

    Banerjee, A. N.; Krishna, R.; Das, B.

    2008-02-01

    In this paper we have reported the syntheses of copper and silicon nano-clusters by a sputtering-gas-aggregation type growth technique. The process involves typical magnetron sputtering vaporization of target materials followed by an inert gas condensation to form clusters of varying sizes. The size-distributions of the clusters typically follow a normal-distribution and the peak cluster sizes of the distributions depends on several factors, which include gas-flow rate, length of the growth region, deposition pressure etc. We have observed a variation in the peak cluster size with the variation of the gas (argon) flow rates. The experimental values are compared with the existing models and the results are found to be in good agreement. The results are significant since it demonstrates that proper optimization of operation conditions can lead to desired cluster sizes as well as desired cluster-size distributions.

  20. Development of metal cluster-based energetic materials at NSWC-IHD

    NASA Astrophysics Data System (ADS)

    Lightstone, James; Stoltz, Chad; Wilson, Rebecca M.; Horn, Jillian M.; Hooper, Joe; Mayo, Dennis; Eichhorn, Bryan; Bowen, Kit H.; White, Michael G.

    2012-03-01

    Current research efforts at NSWC-IHD are utilizing gas-phase molecular beam studies, theoretical calculations, and condensed-phase production methods to identify novel metal cluster systems in which passivated metal clusters make up the subunit of a molecular metal-based energetic material. The reactivity of NixAly+ clusters with nitromethane was investigated using a gas-phase molecular beam system. Results indicate that nitromethane is highly reactive toward the NixAly+ clusters and suggests it would not make a good passivating ligand for these cluster systems. To date, small amounts of a metal-based compound with a subunit containing four aluminum atoms and four Cp* ligands has been produced and was characterized using DSC and TGA. Results indicate this cluster material is more reactive than micron- and nano-sized aluminum. However lack of stability in air precludes it from being a viable replacement for current aluminum particles. Volumetric heat of combustion of Al50Cp*12 was determined using thermodynamic data obtained from first principles calculations. The Al50 cluster is found to have a heat of combustion near 60% that of pure aluminum.

  1. Functionally Graded Materials by Laser Metal Deposition (PREPRINT)

    DTIC Science & Technology

    2010-03-01

    equilibrium phase diagram (Fig. 2(a)) shows σ-phase is more likely to form in austenitic steels when there is ferrite retained from high temperature ... temperature during the entire deposition process. Table 6 shows the process parameters of powder-2 deposit on (with/without pre-heat) Ti6Al4V ...laser-rapid forming (LRF), etc. like Ti-N [5,6,7]; Ti-C-N [8], Ti-Al [9]; SiCp- Ti6Al4V [10]; TiC- Ti6Al4V and TiC+NiCrBSi – Ti6Al4V [11]; Ti-xV, Ti

  2. Chemical bonding and aromaticity in trinuclear transition-metal halide clusters.

    PubMed

    Weck, Philippe F; Sergeeva, Alina P; Kim, Eunja; Boldyrev, Alexander I; Czerwinski, Kenneth R

    2011-02-07

    Trinuclear transition-metal complexes such as Re(3)X(9) (X = Cl, Br, I), with their uniquely featured structure among metal halides, have posed intriguing questions related to multicenter electron delocalization for several decades. Here we report a comprehensive study of the technetium halide clusters [Tc(3)(μ-X)(3)X(6)](0/1-/2-) (X = F, Cl, Br, I), isomorphous with their rhenium congeners, predicted from density functional theory calculations. The chemical bonding and aromaticity in these clusters are analyzed using the recently developed adaptive natural density partitioning method, which indicates that only [Tc(3)X(9)](2-) clusters exhibit aromatic character, stemming from a d-orbital-based π bond delocalized over the three metal centers. We also show that standard methods founded on the nucleus-independent chemical shift concept incorrectly predict the neutral Tc(3)X(9) clusters to be aromatic.

  3. Theoretical research program to study transition metal trimers and embedded clusters

    NASA Technical Reports Server (NTRS)

    Walch, S. P.

    1985-01-01

    Small transition metal clusters at a high level of approximation i.e. including all the valence electrons in the calculation and also including extensive electron correlation were studied. Perhaps the most useful end result of these studies is the qualitative information about the electronic structure of these small metal clusters, including the nature of the bonding. The electronic structure studies of the small clusters are directly applicable to problems in catalysis. From comparison of dimers, trimers and possibly higher clusters, it is possible to extrapolate the information obtained to provide insights into the electronic structure of bulk transition metals and their interaction with other atoms and molecules at both surface and interior locations.

  4. Intrinsic Magnetic Properties of fct FePt Nanocubes and Rods by Cluster Beam Deposition

    NASA Astrophysics Data System (ADS)

    Akdogan, Ozan; Li, Wanfeng; Hadjipanayis, George; Skomski, Ralph; Sellmyer, David

    2012-02-01

    In this work, single crystal fct FePt nanocubes have been successfully produced by a cluster beam deposition technique without the need of post annealing. Particles have been deposited by DC magnetron sputtering using high Ar pressures (0.5 to 2 Torr) on both single crystal Si substrates and Au grids for the measurement of magnetic and structural properties, respectively. The nanocubes have a uniform size distribution with an average size of 6.5 nm. At 1 Torr, the particles have the fct structure with an order parameter of 0.5 and a RT coercivity of 2 kOe with high switching fields seen in the hysteresis loop. Particle size was controlled by changing the pressure and power and also by ex-situ annealing. In addition to these nanocubes, micron size rods (which consist of 20 nm nanoparticles) with the fct structure have been observed near the cluster gun. These particles show a room temperature coercivity of 8 kOe with an order parameter of 0.85. Intrinsic magnetic properties (Curie temperature, HA, MS and magnetic viscosity) of the nanocubes and the nanoparticles (separated from the rods) have been extensively studied and the results will be reported.

  5. Hybrid nanocomposite coatings from metal (Mg alloy)-drug deposited onto medical implant by laser adaptive ablation deposition technique

    NASA Astrophysics Data System (ADS)

    Serbezov, Valery; Sotirov, Sotir; Serbezov, Svetlin

    2013-03-01

    Drug-eluting medical implants are active implants whose function is to create healing effects. The current requirements for active medical coatings for Drug-eluting medical implants are to be biocompatible, biodegradable, polymer free, mechanically stable and enable a controlled release of one or more drugs and defined degradation. This brings hybrid nanocomposite coatings into focus especially in the field of cardiovascular implants. We studied the properties of Metal (Mg alloy)-Paclitaxel coatings obtained by novel Laser Adaptive Ablation Deposition Technique (LAAD) onto cardiovascular stents from 316 LVM stainless steel material. The morphology and topology of coatings were studied by Bright field / Fluorescence optical microscope and Scanning Electron Microscope (SEM). Comparative measurements were made of the morphology and topology of hybrid, polymer free nanocomposite coatings deposited by LAAD and polymerdrug coatings deposited by classical spray technique. The coatings obtained by LAAD are homogeneous without damages and cracks. Metal nanoparticles with sizes from 40 nm to 230 nm were obtained in drug matrixes. Energy Dispersive X-ray Spectroscopy (EDX) was used for identification of metal nanoparticles presence in hybrid nanocomposites coatings. The new technology opens up possibilities to obtain new hybrid nanocomposite coatings with applications in medicine, pharmacy and biochemistry.

  6. Bonding study in all-metal clusters containing Al4 units.

    PubMed

    Mandado, Marcos; Krishtal, Alisa; Van Alsenoy, Christian; Bultinck, Patrick; Hermida-Ramón, J M

    2007-11-22

    The nature of the bonding of a series of gas-phase all-metal clusters containing the Al4 unit attached to an alkaline, alkaline earth, or transition metal is investigated at the DFT level using Mulliken, quantum theory of atoms in molecules (QTAIM), and Hirshfeld iterative (Hirshfeld-I) atomic partitionings. The characterization of ionic, covalent, and metallic bonds is done by means of charge polarization and multicenter electron delocalization. This Article uses for the first time Hirshfeld-I multicenter indices as well as Hirshfeld-I based atomic energy calculations. The QTAIM charges are in line with the electronegativity scale, whereas Hirshfeld-I calculations display deviations for transition metal clusters. The Mulliken charges fail to represent the charge polarization in alkaline metal clusters. The large ionic character of Li-Al and Na-Al bonds results in weak covalent bonds. On the contrary, scarcely ionic bonds (Be-Al, Cu-Al and Zn-Al) display stronger covalent bonds. These findings are in line with the topology of the electron density. The metallic character of these clusters is reflected in large 3-, 4- and 5-center electron delocalization, which is found for all the molecular fragments using the three atomic definitions. The previously reported magnetic inactivity (based on means of magnetic ring currents) of the pi system in the Al42- cluster contrasts with its large pi electron delocalization. However, it is shown that the different results not necessary contradict each other.

  7. The Photo-Electric Effect in Metallic Clusters

    NASA Astrophysics Data System (ADS)

    Krc, Eugene

    Small clusters of Silver atoms have been observed to yield about 100 times more photo-electrons than crystalline Silver (per unit area of surface) for photons with energy up to 1.5 ev above threshold. I have calculated the yield from Silver and Sodium clusters of up to 55 atoms using a Green's function formalism. A method of successive approximations takes into account the scattering of the electrons by the ion-cores as well as by the surface. The formalism is applied to an independent-electron model with a muffin -tin potential. Each electron feels the incident light wave and the polarization field of all the other electrons computed with the bulk dielectric function. Scattering of the photo-excited electron is included as a final step in the photo-emission process. The cross-sections calculated for Silver clusters are in good agreement with experiment; for Sodium clusters, however, the relevant experimental data are incomplete.

  8. Age and metallicity of star clusters in the Small Magellanic Cloud from integrated spectroscopy

    NASA Astrophysics Data System (ADS)

    Dias, B.; Coelho, P.; Barbuy, B.; Kerber, L.; Idiart, T.

    2010-09-01

    Context. Analysis of ages and metallicities of star clusters in the Magellanic Clouds provide information for studies on the chemical evolution of the Clouds and other dwarf irregular galaxies. Aims: The aim is to derive ages and metallicities from integrated spectra of 14 star clusters in the Small Magellanic Cloud, including a few intermediate/old age star clusters. Methods: Making use of a full-spectrum fitting technique, we compared the integrated spectra of the sample clusters to three different sets of single stellar population models, using two fitting codes available in the literature. Results: We derive the ages and metallicities of 9 intermediate/old age clusters, some of them previously unstudied, and 5 young clusters. Conclusions: We point out the interest of the newly identified as intermediate/old age clusters HW1, NGC 152, Lindsay 3, Lindsay 11, and Lindsay 113. We also confirm the old ages of NGC 361, NGC 419, Kron 3, and of the very well-known oldest SMC cluster, NGC 121. Appendix A is only available in electronic form at http://www.aanda.org

  9. Nucleoside modification with boron clusters and their metal complexes.

    PubMed

    Wojtczak, Blazej A; Olejniczak, Agnieszka B; Lesnikowski, Zbigniew J

    2009-09-01

    General methods for the synthesis of nucleosides modified with borane clusters and metallacarborane complexes are presented. These include: (1) the click chemistry approach based on Huisgen 1,3-dipolar cycloaddition and (2) tethering of the metallacarborane group to the aglycone of a nucleoside via a dioxane ring opening in oxonium metallacarborane derivatives. The proposed methodologies broaden the availability of nucleoside-borane cluster conjugates and open up new areas for their applications.

  10. Nonlinear Color--Metallicity Relations of Globular Clusters. VI. On Calcium II Triplet Based Metallicities of Globular Clusters in Early-type Galaxies

    NASA Astrophysics Data System (ADS)

    Chung, Chul; Yoon, Suk-Jin; Lee, Sang-Yoon; Lee, Young-Wook

    2016-02-01

    The metallicity distribution function of globular clusters (GCs) in galaxies is a key to understanding galactic formation and evolution. The calcium II triplet (CaT) index has recently become a popular metal abundance indicator thanks to its sensitivity to GC metallicity. Here we revisit and assess the reliability of CaT as a metallicity indicator using our new stellar population synthesis simulations based on empirical high-resolution fluxes. The model shows that the CaT strength of old (>10 Gyr) GCs is proportional to [Fe/H] below -0.5. In the modest metal-rich regime, however, CaT does not increase anymore with [Fe/H] due to the little contribution from coolest red giant stars to the CaT absorption. The nonlinear nature of the color-CaT relation is confirmed by the observations of GCs in nearby early-type galaxies. This indicates that the CaT should be used carefully when deriving metallicities of metal-rich stellar populations. Our results offer an explanation for the observed sharp difference between the color and CaT distributions of GCs in the same galaxies. We take this as an analogy to the view that metallicity-color and metallicity-Lick index nonlinearity of GCs is primarily responsible for their observed “bimodal” distributions of colors and absorption indices.

  11. Gold, base-metal, and related deposits of North Carolina

    USGS Publications Warehouse

    Luttrell, Gwendolyn Werth

    1978-01-01

    Gold, silver, copper, lead, zinc, pyrite, tin, cobalt, molybdenum, tungsten, barite, and rare-earths have been mined in North Carolina. Gold, with by-product silver, occurs in veins and mineralized shear zones in metamorphic rocks of the Piedmont province and in placers derived from these deposits. Copper occurs with complex sulfide ores in quartz veins in the metamorphic rocks of the Piedmont province and in massive pyrrhotite-pyrite deposits in crystalline rocks west of the Blue Ridge. Lead and zinc occur in complex ores of gold, copper, lead, zinc, and silver in veins and replacements in metamorphic rocks. Pyrite occurs in crystalline metamorphic rocks. Tin occurs in pegmatite and placer deposits in crystalline rocks near Kings Mountain. Cobalt minerals with ores of iron or gold have been reported in a few areas in the Piedmont. Molybdenum occurs along the borders of a granite body in Halifax County. Tungsten minerals occur with copper sulfide ores in Cabarrus and Vance Counties. Barite occurs in quartz veins and associated with sulfide minerals in Orange, Madison, Cleveland, and Gaston Counties. Ore-earths occur with sulfides in vein deposits in Cabarrus County.

  12. Dispersed metal cluster catalysts by design. Synthesis, characterization, structure, and performance

    SciTech Connect

    Arslan, Ilke; Dixon, David A.; Gates, Bruce C.; Katz, Alexander

    2015-09-30

    To understand the class of metal cluster catalysts better and to lay a foundation for the prediction of properties leading to improved catalysts, we have synthesized metal catalysts with well-defined structures and varied the cluster structures and compositions systematically—including the ligands bonded to the metals. These ligands include supports and bulky organics that are being tuned to control both the electron transfer to or from the metal and the accessibility of reactants to influence catalytic properties. We have developed novel syntheses to prepare these well-defined catalysts with atomic-scale control the environment by choice and placement of ligands and applied state-of-the art spectroscopic, microscopic, and computational methods to determine their structures, reactivities, and catalytic properties. The ligands range from nearly flat MgO surfaces to enveloping zeolites to bulky calixarenes to provide controlled coverages of the metal clusters, while also enforcing unprecedented degrees of coordinative unsaturation at the metal site—thereby facilitating bonding and catalysis events at exposed metal atoms. With this wide range of ligand properties and our arsenal of characterization tools, we worked to achieve a deep, fundamental understanding of how to synthesize robust supported and ligand-modified metal clusters with controlled catalytic properties, thereby bridging the gap between active site structure and function in unsupported and supported metal catalysts. We used methods of organometallic and inorganic chemistry combined with surface chemistry for the precise synthesis of metal clusters and nanoparticles, characterizing them at various stages of preparation and under various conditions (including catalytic reaction conditions) and determining their structures and reactivities and how their catalytic properties depend on their compositions and structures. Key characterization methods included IR, NMR, and EXAFS spectroscopies to identify

  13. Synthesis and stabilization of supported metal catalysts by atomic layer deposition.

    PubMed

    Lu, Junling; Elam, Jeffrey W; Stair, Peter C

    2013-08-20

    Supported metal nanoparticles are among the most important catalysts for many practical reactions, including petroleum refining, automobile exhaust treatment, and Fischer-Tropsch synthesis. The catalytic performance strongly depends on the size, composition, and structure of the metal nanoparticles, as well as the underlying support. Scientists have used conventional synthesis methods including impregnation, ion exchange, and deposition-precipitation to control and tune these factors, to establish structure-performance relationships, and to develop better catalysts. Meanwhile, chemists have improved the stability of metal nanoparticles against sintering by the application of protective layers, such as polymers and oxides that encapsulate the metal particle. This often leads to decreased catalytic activity due to a lack of precise control over the thickness of the protective layer. A promising method of catalyst synthesis is atomic layer deposition (ALD). ALD is a variation on chemical vapor deposition in which metals, oxides, and other materials are deposited on surfaces by a sequence of self-limiting reactions. The self-limiting character of these reactions makes it possible to achieve uniform deposits on high-surface-area porous solids. Therefore, design and synthesis of advanced catalysts on the nanoscale becomes possible through precise control over the structure and composition of the underlying support, the catalytic active sites, and the protective layer. In this Account, we describe our advances in the synthesis and stabilization of supported metal catalysts by ALD. After a short introduction to the technique of ALD, we show several strategies for metal catalyst synthesis by ALD that take advantage of its self-limiting feature. Monometallic and bimetallic catalysts with precise control over the metal particle size, composition, and structure were achieved by combining ALD sequences, surface treatments, and deposition temperature control. Next, we describe

  14. Generation and characterization of alkali metal clusters in Y-FAU zeolites. An ESR and MAS NMR spectroscopic study

    NASA Astrophysics Data System (ADS)

    Hannus, István; Béres, Attila; Nagy, János B.; Halász, János; Kiricsi, Imre

    1997-06-01

    Charged and neutral metal clusters of various compositions and sizes can be prepared by controlling the alkali metal content by the decomposition of alkali azides and the composition of the host zeolite by ion-exchange. ESR signals show that electron transfer from alkali metal atoms to alkali metal cations does occur, but in a direction opposite to that predicted by the gas-phase thermochemistry. Alkali metal clusters proved to be very active basic catalytic centers.

  15. The inhomogeneous reionization of the local intergalactic medium by metal-poor globular clusters

    NASA Astrophysics Data System (ADS)

    Griffen, B. F.; Drinkwater, M. J.; Iliev, Ilian T.; Thomas, P. A.; Mellema, Garrelt

    2013-06-01

    We present detailed radiative transfer simulations of the reionization of the Milky Way by metal-poor globular clusters. We identify potential metal-poor globular cluster candidates within the Aquarius simulation using dark matter halo velocity dispersions. We calculate the local ionization fields via a photon-conserving, three dimensional non-equilibrium chemistry code. The key feature of the model is that globular cluster formation is suppressed if the local gas is ionized. We assume that at these early times, the ionization field is dominated by the flux from metal-poor globular clusters. Our spatial treatment of the ionization field leads to drastically different numbers and spatial distributions when compared to models where globular cluster formation is simply truncated at early redshifts (z ˜ 13). The spatial distributions are more extended and more globular clusters are produced. We find that additional sources of ionization are required at later epochs (z ˜ 10) to ionize the remaining gas and recover radial distributions statistically consistent with that of the Milky Way metal-poor globular clusters. We investigate a range of plausible ionization efficiencies to determine the effect photon-rich and photon-poor models have on present-day globular cluster properties. If globular clusters do indeed form within high-redshift dark matter haloes, they produce enough photons to ionize 98 and 90 per cent local (i.e. 23 h-3 Mpc3 centred on the host galaxy) volume and mass by redshift 10, respectively. In our photon-poorest model, this contribution drops to 60 and 50 per cent. Our model therefore implies that globular clusters are important contributors to the reionization process on local scales at high-redshift until more photon-rich sources dominate the photon budget at later times. The surviving clusters in all models have a narrow average age range (mean = 13.34 Gyr, σ = 0.04 Gyr) consistent with current age estimates of the Milky Way metal-poor globular

  16. Metal dust deposition in a shotgun wound associated with barrel modification.

    PubMed

    Williams, Andrew S; Bowes, Matthew J

    2016-03-01

    Contact-range gunshot wounds commonly demonstrate deposition of black soot in and around the wound. Deposition of other visible pigments originating from the firearm has not been specifically described. In the current case, an adult male was found dead adjacent to a shotgun fixed in a vice grip with a modified, shortened barrel. A handheld, powered, metal grinding wheel was nearby. Autopsy revealed an intraoral gunshot wound, including soot deposition in and around the mouth and within the wound track. In addition, there was a peculiar, gray, lustrous film on the lips, gingiva, and anterior teeth. The material was concentrated around the most severe areas of injury in the anterior mouth and easily rubbed off with a cotton swab. It was not visualized in the rest of the mouth and not present in the larynx, or the esophagus. Overall, our opinion is that this unique, gray, lustrous film represents deposition of fine metallic dust that accumulated in the barrel of the shotgun during its modification with the grinding wheel. This type of unique pigment deposition should be recognized by forensic pathologists as possibly being related to the discharge of a firearm with a recently modified barrel or other cause for fine metallic dust accumulation within the barrel. Depending on the circumstances of the case, collection of samples of such metal dust deposits could be indicated for subsequent analysis.

  17. Experimental study of fractal clusters formation from nanoparticles synthesized by atmospheric pressure plasma-enhanced chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Mishin, Maxim V.; Protopopova, Vera S.; Alexandrov, Sergey E.

    2014-11-01

    This paper presents the experimental results from the fractal structures formation from nanoparticles of silicone dioxide deposited on the silicon substrate surface. Nanoparticles are synthesized by atmospheric pressure plasma-enhanced chemical vapor deposition with the use of capacitively coupled radio frequency (13.56 MHz) discharge sustained in helium atmosphere. Tetraethoxysilane is chosen as the test precursor. Correlation between the morphology of obtained deposits and the process parameters is found. The capability of nanoparticles movement along the deposit surface in local near-surface electric field is demonstrated. The empirical model that satisfactorily explained the mechanism of fractal clusters formation from nanoparticles on the substrate surface is developed. The model indicates that the dynamics of deposit morphology variations is determined by two competing processes: electrical charge transfer by nanoparticles to the deposit surface and electrical charge running off over the surface under conditions of changeable conductivity of the deposit surface.

  18. ZnO deposition on metal substrates: Relating fabrication, morphology, and wettability

    NASA Astrophysics Data System (ADS)

    Beaini, Sara S.; Kronawitter, Coleman X.; Carey, Van P.; Mao, Samuel S.

    2013-05-01

    It is not common practice to deposit thin films on metal substrates, especially copper, which is a common heat exchanger metal and practical engineering material known for its heat transfer properties. While single crystal substrates offer ideal surfaces with uniform structure for compatibility with oxide deposition, metallic surfaces needed for industrial applications exhibit non-idealities that complicate the fabrication of oxide nanostructure arrays. The following study explored different ZnO fabrication techniques to deposit a (super)hydrophobic thin film of ZnO on a metal substrate, specifically copper, in order to explore its feasibility as an enhanced condensing surface. ZnO was selected for its non-toxicity, ability to be made (super)hydrophobic with hierarchical roughness, and its photoinduced hydrophilicity characteristic, which could be utilized to pattern it to have both hydrophobic-hydrophilic regions. We investigated the variation of ZnO's morphology and wetting state, using SEMs and sessile drop contact angle measurements, as a function of different fabrication techniques: sputtering, pulsed laser deposition (PLD), electrodeposition and annealing Zn. We successfully fabricated (super)hydrophobic ZnO on a mirror finish, commercially available copper substrate using the scalable electrodeposition technique. PLD for ZnO deposition did not prove viable, as the ZnO samples on metal substrates were hydrophilic and the process does not lend itself to scalability. The annealed Zn sheets did not exhibit consistent wetting state results.

  19. Ligand-modified metal clusters for gas separation and purification

    DOEpatents

    Okrut, Alexander; Ouyang, Xiaoying; Runnebaum, Ron; Gates, Bruce C.; Katz, Alexander

    2017-02-21

    Provided is an organic ligand-bound metal surface that selects one gaseous species over another. The species can be closely sized molecular species having less than 1 Angstrom difference in kinetic diameter. In one embodiment, the species comprise carbon monoxide and ethylene. Such organic ligand-bound metal surfaces can be successfully used in gas phase separations or purifications, sensing, and in catalysis.

  20. Dialkyldiselenophosphinato-metal complexes - a new class of single source precursors for deposition of metal selenide thin films and nanoparticles

    NASA Astrophysics Data System (ADS)

    Malik, Sajid N.; Akhtar, Masood; Revaprasadu, Neerish; Qadeer Malik, Abdul; Azad Malik, Mohammad

    2014-08-01

    We report here a new synthetic approach for convenient and high yield synthesis of dialkyldiselenophosphinato-metal complexes. A number of diphenyldiselenophosphinato-metal as well as diisopropyldiselenophosphinato-metal complexes have been synthesized and used as precursors for deposition of semiconductor thin films and nanoparticles. Cubic Cu2-xSe and tetragonal CuInSe2 thin films have been deposited by AACVD at 400, 450 and 500 °C whereas cubic PbSe and tetragonal CZTSe thin films have been deposited through doctor blade method followed by annealing. SEM investigations revealed significant differences in morphology of the films deposited at different temperatures. Preparation of Cu2-xSe and In2Se3 nanoparticles using diisopropyldiselenophosphinato-metal precursors has been carried out by colloidal method in HDA/TOP system. Cu2-xSe nanoparticles (grown at 250 °C) and In2Se3 nanoparticles (grown at 270 °C) have a mean diameter of 5.0 ± 1.2 nm and 13 ± 2.5 nm, respectively.

  1. Thin films of metal oxides grown by chemical vapor deposition from volatile transition metal and lanthanide metal complexes

    NASA Astrophysics Data System (ADS)

    Pollard, Kimberly Dona

    1998-08-01

    This thesis describes the synthesis and characterization of novel volatile metal-organic complexes for the chemical vapor deposition (CVD) of metal oxides. Monomeric tantalum complexes, lbrack Ta(OEt)sb4(beta-diketonate)) are prepared by the acid-base reaction of lbrack Tasb2(OEt)sb{10}rbrack with a beta-diketone, (RC(O)CHsb2C(O)Rsp' for R = CHsb3, Rsp' = CFsb3; R = Rsp'=C(CHsb3)sb3; R = Csb3Fsb7,\\ Rsp'=C(CHsb3)sb3;\\ R=Rsp'=CFsb3; and R = Rsp' = CHsb3). The products are characterized spectroscopically. Thermal CVD using these complexes as precursors gave good quality Tasb2Osb5 thin films which are characterized by XPS, SEM, electrical measurements, and XRD. Factors affecting the film deposition such as the type of carrier gas and the temperature of the substrate were considered. Catalyst-enhanced CVD reactions with each of the precursors and a palladium catalyst, ((2-methylallyl)Pd(acac)), were studied as a lower temperature route to good quality Tasb2Osb5 films. The decomposition mechanism at the hot substrate surface was studied. Precursors for the formation of yttria by CVD were examined. New complexes of the form (Y(hfac)sb3(glyme)), (hfac = \\{CFsb3C(O)CHC(O)CFsb3\\}sp-,\\ glyme=CHsb3O(CHsb2CHsb2O)sb{n}CHsb3 for n = 1-4) were synthesized and characterized spectroscopically. X-ray structural determinations of three new complexes were obtained. CVD reaction conditions were determined which give YOF films and, with catalyst-enhanced CVD, reaction conditions which give selective formation of Ysb2Osb3, YOF, or YFsb3. The films were studied by XPS, SEM, and XRD. Decomposition mechanisms which lead to film formation, together with a possible route for fluorine atom transfer from the ligand to the metal resulting in fluorine incorporation, were studied by analysis of exhaust products using GC-MS. Novel precursors of the form lbrack Ce(hfac)sb3(glyme)rbrack,\\ (hfac=\\{CFsb3C(O)CHC(O)CFsb3\\}sp-,\\ glyme=CHsb3O(CHsb2CHsb2O)sb{n}CHsb3, n = 1-4) for CVD of ceria were

  2. Introduction: advances and opportunities in cluster research. [Neutral (metal) and ionic clusters

    SciTech Connect

    Castleman, A.W. Jr.

    1983-01-01

    Examples of neutral and ionic clusters include these in the upper and lower atmosphere, interstellar grain formation, combustion, radiation physics and chemistry, surface bombardment, fission product transport in reactors, corrosion, etc. This paper is a brief overview of some recent developments in cluster research. (DLC)

  3. Photoemission Studies of Metallic Photocathodes Prepared by Pulsed Laser Ablation Deposition Technique

    SciTech Connect

    Fasano, V.; Lorusso, A.; Perrone, A.; De Rosa, H.; Cultrera, L.

    2010-11-10

    We present the results of our investigation on metallic films as suitable photocathodes for the production of intense electron beams in RF photoinjector guns. Pulsed laser ablation deposition technique was used for growing Mg and Y thin films onto Si and Cu substrates in high vacuum and at room temperature.Different diagnostic methods were used to characterize the thin films deposited on Si with the aim to optimize the deposition process. Photoelectron performances were investigated on samples deposited on Cu substrate in an ultra high vacuum photodiode chamber at 10{sup -7} Pa. Relatively high quantum efficiencies have been obtained for the deposited films, comparable to those of corresponding bulks. Samples could stay for several months in humid open air before being tested in a photodiode cell. The deposition process and the role of the photocathode surface contamination and its influence on the photoelectron performances are presented and discussed.

  4. A DFT study of Ni clusters deposition on titania and zirconia (101) surfaces

    NASA Astrophysics Data System (ADS)

    Tosoni, Sergio; Chen, Hsin-Yi Tiffany; Pacchioni, Gianfranco

    2016-04-01

    Density functional calculations are employed to simulate the deposition of an isolated Ni atom and a Ni10 particle on the stoichiometric and reduced anatase TiO2 (101) and tetragonal ZrO2 (101) surfaces. The main purpose of this work is to study the modification of the electronic structure of the oxide induced by the metal, aiming at the understanding of the physical properties of new catalysts for biomass conversion. When the adsorption of a Ni atom takes place on stoichiometric surfaces, no major charge transfer is observed. On reduced titania, and more pronouncedly on reduced zirconia, the Ni atom is negatively charged, provided that the vacancy is in direct contact with the adsorbed metal atom. For Ni10, on titania the bonding is dominated by the hybridization of the metal and the oxide states but we did not find evidence for a direct reduction of the oxide via formation of Ti3 + states. For Ni10 on zirconia, the metal particle is positively charged on the stoichiometric surface and negatively charged on the reduced one but, again, there is no indication of a direct reduction of the oxide. Finally, the reverse oxygen spillover is considered as a possible route to reduce the oxide support. The result is that Ni10 promotes oxygen spillover on titania almost spontaneously, while on zirconia this process is thermodynamically unfavourable.

  5. Ultrathin metallic interlayers in vacuum deposited MoOx/metal/MoOx electrodes for organic solar cells

    NASA Astrophysics Data System (ADS)

    Travkin, V. V.; Luk'yanov, A. Yu.; Drozdov, M. N.; Vopilkin, E. A.; Yunin, P. A.; Pakhomov, G. L.

    2016-12-01

    Eight types of practically important metals were tested as interlayers in MoOx/Metal/MoOx composite electrodes. Ultrathin semitransparent electrodes with a fixed thickness were deposited on glass, using thermal vacuum evaporation, and characterized by various microscopic and X-ray techniques and by mass spectrometry profiling. The optical transmission and sheet resistance of the electrodes were compared as key parameters for photovoltaic applications. We attempted to find correlations between the chemical properties of embedded metals and the structural/conducting properties of composite electrodes. In general, the electrodes with noble metal interlayers feature a better conductivity, whereas their average transparency in the visible and near infrared range is similar to that of electrodes with reactive metals. Diffusion and oxidation processes in composite electrodes were examined by the SIMS depth profiling technique.

  6. Age and metallicity of star clusters in the Small Magellanic Cloud from integrated spectroscopy

    NASA Astrophysics Data System (ADS)

    Dias, Bruno; Coelho, Paula; Kerber, Leandro; Barbuy, Beatriz; Idiart, Thais

    2010-04-01

    Analysis of integrated spectra of star clusters in the Magellanic Clouds can bring important information for studies on the chemical evolution of the Clouds. The aim of the present work is to derive ages and metallicities from integrated spectra of 15 star clusters in the Small Magellanic Cloud (SMC), some of them not studied so far. Making use of a full spectrum fitting technique, we compared the integrated spectra of the sample clusters to three different sets of single stellar population models available in the literature. We derived ages and metallicities for the sample clusters employing the codes STARLIGHT and ULySS. Out of the 15 clusters in our sample, 9 are old/intermediate age clusters and 6 are young clusters. We point out the results for the newly identified as old/intermediate age clusters HW1, NGC 152, Lindsay 3 and 11. We also confirm old ages for NGC 361, NGC 419 and Kron 3, and the oldest well-known SMC cluster NGC 121.

  7. Effects of deposition of heavy-metal-polluted harbor mud on microbial diversity and metal resistance in sandy marine sediments.

    PubMed

    Toes, Ann-Charlotte M; Finke, Niko; Kuenen, J Gijs; Muyzer, Gerard

    2008-10-01

    Deposition of dredged harbor sediments in relatively undisturbed ecosystems is often considered a viable option for confinement of pollutants and possible natural attenuation. This study investigated the effects of deposition of heavy-metal-polluted sludge on the microbial diversity of sandy sediments during 12 months of mesocosm incubation. Geochemical analyses showed an initial increase in pore-water metal concentrations, which subsided after 3 months of incubation. No influence of the deposited sediment was observed in denaturing gradient gel electrophoresis (DGGE) profiles of bacterial 16S rRNA genes, whereas a minor, transient impact on the archaeal community was revealed. Phylogenetic analyses of bacterial 16S rRNA clone libraries showed an abundance of members of the Flavobacteriaceae, the alpha- and gamma-Proteobacteria, in both the muddy and the sandy sediments. Despite the finding that some groups of clones were shared between the metal-impacted sandy sediment and the harbor control, comparative analyses showed that the two sediments were significantly different in community composition. Consequences of redeposition of metal-polluted sediment were primarily underlined with cultivation-dependent techniques. Toxicity tests showed that the percentage of Cd- and Cu-tolerant aerobic heterotrophs was highest among isolates from the sandy sediment with metal-polluted mud on top.

  8. Grazing-incidence metal deposition: Pattern formation and slope selection

    NASA Astrophysics Data System (ADS)

    van Dijken, Sebastiaan; Jorritsma, Louis C.; Poelsema, Bene

    2000-05-01

    Molecular beam epitaxy of Cu on Cu(001) at grazing angles of incidence has been studied using spot profile analysis low-energy electron diffraction. At angles of incidence larger than 50° the evolving surface morphology no longer shows the fourfold symmetry inherent to Cu(001), leaving only the plane of incidence as a mirror plane. The surface roughness as well as the slope of the grown mound structures increase with increasing deposition angle. These findings are explained by steering, which originates from long-range attractive forces between incident atoms and substrate atoms and leads to preferential arrival of atoms on top of islands. Steering is of general importance and should routinely be considered in growth studies when the angle of incidence of the depositing beam is larger than 50°.

  9. Metal roof corrosion related to volcanic ash deposition

    NASA Astrophysics Data System (ADS)

    Oze, C.; Cole, J. W.; Scott, A.; Wilson, T.; Wilson, G.; Gaw, S.; Hampton, S.; Doyle, C.; Li, Z.

    2013-12-01

    Volcanoes produce a wide range of hazards capable of leading to increased rates of corrosion to the built environment. Specifically, widely distributed volcanic ash derived from explosive volcanic eruptions creates both short- and long-term hazards to infrastructure including increased corrosion to exposed building materials such as metal roofing. Corrosion has been attributed to volcanic ash in several studies, but these studies are observational and are beset by limitations such as not accounting for pre-existing corrosion damage and/or other factors that may have also directly contributed to corrosion. Here, we evaluate the corrosive effects of volcanic ash, specifically focusing on the role of ash leachates, on a variety of metal roofing materials via weathering chamber experiments. Weathering chamber tests were carried out for up to 30 days using a synthetic ash dosed with an acidic solution to produce a leachate comparable to a real volcanic ash. Visual, chemical and surface analyses did not definitively identify significant corrosion in any of the test roofing metal samples. These experiments attempted to provide quantitative information with regards to the rates of corrosion of different types of metal roof materials. However, they demonstrate that no significant corrosion was macroscopically or microscopically present on any of the roofing surfaces despite the presence of corrosive salts after a duration of thirty days. These results suggest ash leachate-related corrosion is not a major or immediate concern in the short-term (< 1 month).

  10. Energetics of small clusters of group IB metals (Cu, Ag, and Au) adsorbed on graphene

    NASA Astrophysics Data System (ADS)

    Kaur, Gagandeep; Gupta, Shuchi; Dharamvir, Keya

    2013-06-01

    The 2D structure of graphene maximizes the interaction of adsorbate on the layer. Many experiments have been devised to form stable metallic clusters of different sizes. We study the structure and binding energies of group IB clusters Mn (M=Au, Ag, Cu n=1, 3) adsorbed on graphene using Gupta potential [1] (for M-M interaction) and Lennard-Jones potential [2] (for metal-carbon interaction). The total energy of the system has been obtained by placing each of Mn cluster a certain distance above the graphene sheet at various positions and in various orientations. The minimized energy configurations, for all Mn clusters, lie above the center of a hexagon and parallel to the graphene sheet. Binding energy per atom for Ag and Cu metal clusters are less than those of respective Au indicating the lower stability of Ag/Cu metal-graphene system. Using various energy barriers, we can calculate the energy required to move small cluster from one position of minimum energy to another on graphene.

  11. Formation and properties of metal clusters isolated in helium droplets.

    PubMed

    Tiggesbäumker, Josef; Stienkemeier, Frank

    2007-09-14

    The unique conditions forming atomic and molecular complexes and clusters using superfluid helium nanodroplets have opened up an innovative route for studying the physical and chemical properties of matter on the nanoscale. This review summarizes the specific characteristics of the formation of atomic clusters partly generated far from equilibrium in the helium environment. Special emphasis is on the optical response, electronic properties as well as dynamical processes which are mostly affected by the surrounding quantum matrix. Experiments include the optical induced response of isolated cluster systems in helium under quite different excitation conditions ranging from the linear regime up to the violent interaction with a strong laser field leading to Coulomb explosion and the generation of highly charged atomic fragments. The variety of results on the outstanding properties in the quantum size regime highlights the peculiar capabilities of helium nanodroplet isolation spectroscopy.

  12. Multiscale approaches for simulation of nucleation, growth, and additive chemistry during electrochemical deposition of thin metal films

    NASA Astrophysics Data System (ADS)

    Stephens, Ryan Mark

    Molecularly engineered deposition processes require computational algorithms that efficiently capture phenomena present at widely varying length and time scales. In this work, the island dynamics method was applied to simulation of kinetically-limited metal nucleation and growth by electrodeposition in the presence of additives. The model included additive kinetics, surface diffusion of adatoms, nucleation, and growth. The model was demonstrated for copper deposition in acid sulfate electrolyte containing [bis(3-sulfopropyl)disulfide], polyethylene glycol, and chloride. Simulation results were compared with kinetic Monte Carlo (KMC) calculations and found to be within 1% for fractional coverage values, and within 10% for nucleation density. The computational time was more than 10X faster than comparable KMC simulations over the range studied. The island dynamics algorithm was applied to the electrodeposition of a metal onto a substrate initially configured with an array of hemispherical seed clusters. It was found that the presence of chloride in the model additive system caused high densities of nuclei on the substrate surrounding the initial seed clusters, which led to the formation of a continuous thin metal film. Simulations carried out under low-chloride conditions resulted in the growth only of the initial seed clusters, without significant nucleation or thin film formation. Additional phenomena were explored by linking the molecular scale island dynamics algorithm to a continuum model that described the migration and diffusion in the diffusion layer near the electrode surface. The multiscale linkage allowed simulation of nucleation, growth, and additive chemistry under mass transport limited conditions, including the formation of nucleation exclusion zones surrounding growing nuclei. A two-step approach was used to calculate the spatial distribution of nucleation events on an electrode undergoing deposition by electrolysis under the influence of mass

  13. First examples of hybrids based on polyoxometalates, metal halide clusters and organic ligands

    NASA Astrophysics Data System (ADS)

    Wang, La-Mei; Fan, Yong; Wang, Yan; Xiao, Li-Na; Hu, Yang-Yang; Peng, Yu; Wang, Tie-Gang; Gao, Zhong-Min; Zheng, Da-Fang; Cui, Xiao-Bing; Xu, Ji-Qing

    2012-07-01

    Two new organic-inorganic compounds based on polyoxometalates, metal halide clusters and organic ligands: [BW12O40]2[Cu2(Phen)4Cl](H24, 4'-bpy)4·H3O·5H2O (1) and [HPW12O40][Cd2(Phen)4Cl2](4, 4'-bpy) (2) (Phen=1, 10-phenanthroline, bpy=bipyridine), have been prepared and characterized by IR, UV-vis, XPS, XRD and single crystal X-ray diffraction analyses. Crystal structure analyses reveal that compound 1 is constructed from [BW12O40]5-, metal halide clusters [Cu2(Phen)4Cl]+and 4, 4'-bpy ligands, while compound 2 is constructed from [PW12O40]3-, metal halide cluster [Cd2(Phen)4Cl2]2+ and 4, 4'-bpy ligands. Compound 1 and compound 2 are not common hybrids based on polyoxometalates and metal halide clusters, they also contain dissociated organic ligands, therefore, compound 1 and 2 are the first examples of hybrids based on polyoxometalates, metal halide clusters and organic ligands.

  14. Increased stability in laser metal wire deposition through feedback from optical measurements

    NASA Astrophysics Data System (ADS)

    Heralić, Almir; Christiansson, Anna-Karin; Ottosson, Mattias; Lennartson, Bengt

    2010-04-01

    Robotized laser metal-wire deposition is a fairly new technique being developed at University West in cooperation with Swedish industry for solid freeform fabrication of fully densed metal structures. It is developed around a standard welding cell and uses robotized fiber laser welding and wire filler material together with a layered manufacturing method to create metal structures. In this work a monitoring system, comprising two cameras and a projected laser line, is developed for on-line control of the deposition process. The controller is a combination of a PI-controller for the bead width and a feed-forward compensator for the bead height. It is evaluated through deposition of single-bead walls, and the results show that the process stability is improved when the proposed controller is used.

  15. Electrical contact characteristics of mechanically mated Y Ba Cu O bulks with deposited metal layer

    NASA Astrophysics Data System (ADS)

    Imaizumi, with deposited metal layer T.; Sawa, K.; Tomita, M.; Murakami, M.; Sakai, N.; Hirabayashi, I.

    2005-10-01

    We have measured contact resistances between two bulk YBCO superconductor blocks with the application to a persistent current switch (PCS) in mind. In order to reduce a contact resistance, we deposited indium and silver on the sample surfaces. The resistance was reduced by increasing the thickness of the deposited metal layers, but it saturated when the thickness reached a certain level. The saturation thickness was much smaller in indium than silver. Such a difference is understandable by considering the hardness of these two metals. The resistance was also reduced by increasing the mechanical load. Overloading however caused the coupling of metal layers, resulting in the peeling off of the deposited layers when the switch was opened.

  16. Atmospheric Deposition of Heavy Metals in Soil Affected by Different Soil Uses of Southern Spain

    NASA Astrophysics Data System (ADS)

    Acosta, J. A.; Faz, A.; Martínez-Martínez, S.; Bech, J.

    2009-04-01

    Heavy metals are a natural constituent of rocks, sediments and soils. However, the heavy metal content of top soils is also dependent on other sources than weathering of the indigenous minerals; input from atmospheric deposition seems to be an important pathway. Atmospheric deposition is defined as the process by which atmospheric pollutants are transferred to terrestrial and aquatic surfaces and is commonly classified as either dry or wet. The interest in atmospheric deposition has increased over the past decade due to concerns about the effects of deposited materials on the environment. Dry deposition provides a significant mechanism for the removal of particles from the atmosphere and is an important pathway for the loading of heavy metals into the soil ecosystem. Within the last decade, an intensive effort has been made to determine the atmospheric heavy metal deposition in both urban and rural areas. The main objective of this study was to identification of atmospheric heavy metals deposition in soil affected by different soil uses. Study area is located in Murcia Province (southeast of Spain), in the surroundings of Murcia City. The climate is typically semiarid Mediterranean with an annual average temperature of 18°C and precipitation of 350 mm. In order to determine heavy metals atmospheric deposition a sampling at different depths (0-1 cm, 1-5 cm, 5-15 cm and 15-30 cm) was carried out in 7 sites including agricultural soils, two industrial areas and natural sites. The samples were taken to the laboratory where, dried, passed through a 2 mm sieve, and grinded. For the determination of the moisture the samples were weighed and oven dried at 105 °C for 24 h. The total amounts of metals (Pb, Cu, Pb, Zn, Cd, Mn, Ni and Cr) were determined by digesting the samples with nitric/perchoric acids and measuring with ICP-MS. Results showed that zinc contamination in some samples of industrial areas was detected, even this contamination reaches 30 cm depth; thus it is

  17. Uniformly Dispersed FeOx Atomic Clusters by Pulsed Arc Plasma Deposition: An Efficient Electrocatalyst for Improving the Performance of Li-O2 Battery

    SciTech Connect

    Luo, Xiangyi; Lu, Jun; Sohm, Evan; Ma, Lu; Wu, Tianpin; Wen, Jianguo; Qiu, Dantong; Xu, Yunkai; Ren, Yang; Miller, Dean J.; Amine, Khalil

    2016-07-01

    The present study aims to explore a new method to improve the catalytic activity of non-precious metals, especially in electrochemical reactions. In this study, highly ionized Fe plasma produced by arc discharge uniformly deposit on porous carbon substrate and form atomic clusters by the Pulsed Arc Plasma Deposition technique. The as-prepared FeOx/C material was tested as a cathode material in rechargeable Li-O2 battery under different current rates. The results show a significantly improvement of the battery performance in both cycle life and reaction rate. Furthermore, XRD and SEM results show that the as-prepared cathode material has the ability to stabilize cathode and reduce side reactions, and current rate is a critical factor of the nucleation of the discharge products.

  18. Transport and deposition of heavy metals in the Ross Sea Region, Antarctica

    NASA Astrophysics Data System (ADS)

    Tuohy, Andrea; Bertler, Nancy; Neff, Peter; Edwards, Ross; Emanuelsson, Daniel; Beers, Thomas; Mayewski, Paul

    2015-10-01

    Emissions and long-range transport of toxic metals and metalloids pose a global threat to ecosystems and human health. Global industrialization occurring from the late nineteenth century releases large quantities of pollutants into the Earth's atmosphere. Despite international efforts to mitigate emissions, accumulation of metals is still observed in the most remote regions of the planet. New baseline studies are needed to determine (i) natural background concentration of pollutants, (ii) contributions of anthropogenic emissions, and (iii) potential remobilization of previously deposited metals. Constructing such records requires distinguishing source strength from transport efficiency to the recording site and accounting for local depositional effects. Here we investigate the sensitivity and representation of Southern Hemisphere atmospheric concentrations of heavy metals (Fe, Al, Mn, Pb, Tl, and As) in the Roosevelt Island Climate Evolution (RICE) ice core, a new coastal Antarctic ice core site. Concentration variability with precipitation is explored in daily surface snow samples collected over 70 days, while seasonal deposition is investigated through snow pit sampling. We find that snow sample concentrations increase with particular snow precipitation types (rime and fog) and enhanced meridional atmospheric transport to the site. Snow pit heavy metals peak in summer and also show variable intraannual peaks. Seasonal airmass modeling based on ERA Interim reanalysis data indicates a synoptic shift during the spring and summer months. We conclude that modern heavy metal concentrations are influenced by transport efficiency and scavenging behavior; and thus, time series records from RICE have the potential to provide representative data of regional changes in heavy metals.

  19. Lithium metal protected by atomic layer deposition metal oxide for high performance anodes

    DOE PAGES

    Chen, Lin; Connell, Justin G.; Nie, Anmin; ...

    2017-05-26

    We present that lithium metal is a highly desirable anode material for lithium batteries due to its extremely high theoretical capacity (3860 mA h g-1), low potential (-3.04 V versus standard hydrogen electrode), and low density (0.534 g cm-3). However, dendrite growth during cycling and low coulombic efficiency, resulting in safety hazards and fast battery fading, are huge barriers to commercialization. Herein, we used atomic layer deposition (ALD) to prepare conformal, ultrathin aluminum oxide coatings on lithium. We investigated the growth mechanism during Al2O3 ALD on lithium by in situ quartz crystal microbalance and found larger growth than expected duringmore » the initial cycles. We also discovered that the ALD Al2O3 enhances the wettability of the Li surface towards both carbonate and ether electrolytes, leading to uniform and dense SEI formation and reduced electrolyte consumption during battery operation. Scanning electron microscopy verified that the bare Li surfaces become rough and dendritic after electrochemical cycling, whereas the ALD Al2O3 coated Li surfaces remain smooth and uniform. Analysis of the Li surfaces after cycling using X-ray photoelectron spectroscopy and in situ transmission electron microscopy revealed that the ALD Al2O3 coating remains intact during electrochemical cycling, and that Li ions diffuse through the coating and deposit on the underlying Li. Coin cell testing demonstrated more than two times longer cycling life for the ALD Al2O3 protected Li, and a coulombic efficiency as high as ~98% at a practical current rate of 1 mA cm-2. More significantly, when the electrolyte volume was reduced from 20 to 5 μL, the stabilizing effect of the ALD coating became even more pronounced and the cycling life was around four times longer. Finally, these results indicate that ALD Al2O3 coatings are a promising strategy to stabilize Li anodes for high performance energy storage devices such as Li–S batteries.« less

  20. Interaction between co-deposited metals during stripping voltammetry at boron-doped diamond electrodes.

    PubMed

    Foord, John S; Eaton, Kirk; Hao, Wang; Crossley, Alison

    2005-07-21

    Electrochemical processes, which underlie the use of conductive diamond electrodes for the simultaneous detection of two or more metal ions in solution by anodic stripping voltammetry (ASV), have been investigated. The model analyte system studied contains the two metal species, Ag+(aq) and Pb2+(aq), and the experimental techniques employed include cyclic and square wave voltammetries, along with X-ray photoelectron spectroscopy and secondary electron microscopy. Although the bulk metallic forms of Ag and Pb are immiscible, several interactions in the system between the two metal species present are observed, which significantly influence the electrodeposition and electrodissolution processes which underlie ASV. The subsequent nucleation and growth of a given metal on the electrode surface is enhanced by the presence of the second metal on the surface. The encapsulation of one metal by the other, within the metal particulates that form on the electrode surface, significantly reduces the stripping yield at the potentials characteristic of the individual metals. The stripping potentials are also influenced by bonding interactions between deposited Ag and Pb, which broaden the characteristic stripping peaks in cyclic voltammetry, as well as producing underpotential deposition and stripping. Given these interactions, the extent to which ASV at diamond electrodes can be used to determine the solution concentrations of Ag+(aq) and Pb2+(aq) is considered.

  1. Atmospheric deposition of heavy metals in Wuxi, China: estimation based on native moss analysis.

    PubMed

    Yan, Yun; Zhang, Qiang; Wang, G Geoff; Fang, Yan-Ming

    2016-06-01

    We studied atmospheric deposition of heavy metals in Wuxi, China, using moss (Haplocladium microphyllum and H. angustifolium) as a biomonitoring agent. Moss samples were collected from 49 sites determined by a systematic sampling method. The top layer of soil on each site was also sampled. No significant correlation (P < 0.05) was observed between the moss and soil concentrations for any of the six heavy metal elements (Cd, Cr, Cu, Ni, Pb, and Zn), indicating that the soil substrate had little effect on the heavy metal concentrations in the moss materials. The metal enrichment capacity of the moss material, characterized by the concentration ratio between the moss and soil samples for each heavy metal, was topped by Cd and then followed by Zn, Pb, Cu, Cr, and Ni, respectively. Significant (P < 0.05) correlations were found among the six elements in mosses, suggesting potential anthropogenic inputs of these heavy metal pollutants. Based on concentrations of the heavy metals in mosses and the calculated contamination factors, we evaluated the contamination level of each heavy metal on the 49 sampling sites. Spatial distribution maps of heavy metal deposition for each element were interpolated using ArcGIS 9.0. A total pollution coefficient was calculated for each sampling site to identify the seriously polluted areas in the region.

  2. Microplasmas for direct, substrate-independent deposition of nanostructured metal oxides

    NASA Astrophysics Data System (ADS)

    Mackie, Katherine E.; Pebley, Andrew C.; Butala, Megan M.; Zhang, Jinping; Stucky, Galen D.; Gordon, Michael J.

    2016-07-01

    A general, substrate-independent method for plasma deposition of nanostructured, crystalline metal oxides is presented. The technique uses a flow-through, micro-hollow cathode plasma discharge (supersonic microplasma jet) with a "remote" ring anode to deliver a highly directed flux of growth species to the substrate. A diverse range of nanostructured materials (e.g., CuO, α-Fe2O3, and NiO) can be deposited on any room temperature surface, e.g., conductors, insulators, plastics, fibers, and patterned surfaces, in a conformal fashion. The effects of deposition conditions, substrate type, and patterning on film morphology, nanostructure, and surface coverage are highlighted. The synthesis approach presented herein provides a general and tunable method to deposit a variety of functional and hierarchical metal oxide materials on many different surfaces. High surface area, conversion-type CuO electrodes for Li-ion batteries are demonstrated as a proof-of-concept example.

  3. Determining the availability of sediment-bound trace metals to aquatic deposit-feeding animals

    USGS Publications Warehouse

    Luoma, Samuel N.; Cain, D.J.; Thomson, E.A.; Johansson, C.; Jenne, E.A.; Bryan, G.W.

    1980-01-01

    Physicochemical form affects, by as much as 1000 fold, the uptake rate by deposit-feeding clams of metals bound to sediments. The strength of metal binding to the different sedimentary binding substrates controls this effect. Statistical studies that were spatially intensive (comparing 35 stations in 17 estuaries) and temporally intensive (2 stations through 2 years time) indicate that sediments control the availability of Ag, Cd, Co, Pb, Zn, Fe, and Mn, and possibly Cu to clams and polychaete worms in nature. Metal concentrations removed from sediments by chemical extractants generally follow availability better than do total metal concentrations, but the specific extractant differs among different metals. Concentrations of binding substrates (Fe, Mn, organic carbon, humic substances) also statistically explain a proportion of the variance of metal concentrations in the animals, suggesting that metal partitioning among substrates in sediments is an important control on metal availability. The specific substrates which contribute to availability also differ among metals. Statistical assessment of metal form in sediments suggested that different substrates compete for the partitioning of metals, that each metal is partitioned among a variety of forms in an oxidized sediment, and that partitioning will vary with the physicochemical characteristics of the sediments. (USGS)

  4. Electrochemical Synthesis and Catalytic Properties of Encapsulated Metal Clusters within Zeolitic Imidazolate Frameworks.

    PubMed

    Wang, Pengyuan; Liu, Jia; Liu, Chuanfang; Zheng, Bin; Zou, Xiaoqin; Jia, Mingjun; Zhu, Guangshan

    2016-11-07

    It is very interesting and also a big challenge to encapsulate metal clusters within microporous solids to expand their application diversity. For this target, herein, we present an electrochemical synthesis strategy for the encapsulation of noble metals (Au, Pd, Pt) within ZIF-8 cavities. In this method, metal precursors of AuCl4(2-) , PtCl6(2-) , and PdCl4(2-) are introduced into ZIF-8 crystals during the concurrent crystallization of ZIF-8 at the anode. As a consequence, very small metal clusters with sizes around 1.2 nm are obtained within ZIF-8 crystals after hydrogen reduction; these clusters exhibit high thermal stability, as evident from the good maintenance of their original sizes after a high-temperature test. The catalytic properties of the encapsulated metal clusters within ZIF-8 are evaluated for CO oxidations. Because of the small pore window of ZIF-8 (0.34 nm) and the confinement effect of small pores, about 80 % of the metal clusters (fractions of 0.74, 0.77, and 0.75 for Au, Pt, and Pd in ZIF-8, respectively) retain their catalytic activity after exposure to the organosulfur poison thiophene (0.46 nm), which is in contrast to their counterparts (fractions of 0.22, 0.25, and 0.20 for Au, Pt, and Pd on the SiO2 support). The excellent performances of metal clusters encapsulated within ZIF-8 crystals give new opportunities for catalytic reactions.

  5. Structure and Dynamics in Metal-Containing Clusters

    DTIC Science & Technology

    2010-03-11

    increases but the basic nature of the vibration remains constant. A surprising development followed from this new spectroscopic study of titanium ...establishes that titanium -carbide nanocrystals are seeds present in the early phases of the formation of stardust. Titanium -carbide crystallites are actually...multi-metal sandwiches (M3-coronene2). In some species (e.g., iron with C6o or niobium with coronene), the metal inserts into the organic ring system

  6. Formation of Deep Sea Umber Deposits Linked to Microbial Metal Oxidation at the South Atlantic Ridge

    NASA Astrophysics Data System (ADS)

    Peng, Xiaotong; Ta, Kaiwen; Chen, Shun; Zhang, Lijuan; Xu, Hengchao

    2015-04-01

    Umber deposits are important metalliferous deposits, which occur in off-axis half-graben structures at ancient and modern ocean floor. The genesis of umber deposits has remained controversial for several decades. Recently, microbial Fe(II) oxidation associated with low-temperature diffuse venting has been identified as a key process for the formation of umber deposits, but the exact biochemical mechanisms involved to the precipitation of Mn oxides and co-precipitation of Fe oxyhydroxides and Mn oxides in umber deposits still remain unknown. Here, we used nano secondary ion mass spectrometer, synchrotron-based X-ray absorption spectroscopy, electron microscopy, and molecular techniques to demonstrate the coexistence of two types of metal-oxidizing bacteria within deep-sea hydrothermal umber deposits at the South Atlantic Ridge, where we found unique spheroids composed of biogenic Fe oxyhydroxides and Mn oxides in the deposits. Our data suggest that Fe oxyhydroxides and Mn oxides are metabolic by-products of lithotrophic Fe(II)-oxidizing bacteria and heterotrophic Mn(II)-oxidizing bacteria, respectively. The hydrothermal vents fuel lithotrophic Fe(II)-oxidizing bacteria, which constitute a trophic base that may support the activities of heterotrophic Mn(II)-oxidizing bacteria. The biological origin of umber deposits underscore the importance of geomicrobiologcial interaction in triggering the formation of deep-sea deposits, with important implications for the generation of submarine Mn deposits and crusts.

  7. Monte Carlo simulation of energy-deposit clustering for ions of the same LET in liquid water.

    PubMed

    Francis, Z; Incerti, S; Ivanchenko, V; Champion, C; Karamitros, M; Bernal, M A; El Bitar, Z

    2012-01-07

    This work presents a Monte Carlo study of energy depositions due to protons, alpha particles and carbon ions of the same linear-energy-transfer (LET) in liquid water. The corresponding track structures were generated using the Geant4-DNA toolkit, and the energy deposition spatial distributions were analyzed using an adapted version of the DBSCAN clustering algorithm. Combining the Geant4 simulations and the clustering algorithm it was possible to compare the quality of the different radiation types. The ratios of clustered and single energy depositions are shown versus particle LET and frequency-mean lineal energies. The estimated effect of these types of radiation on biological tissues is then discussed by comparing the results obtained for different particles with the same LET.

  8. Electrochemical Deposition of Metal-ceramic Composite Coating

    NASA Astrophysics Data System (ADS)

    Kan, Hong-Min; Feng, Xiao-Jun; Wu, Yuan-Yuan; Tian, Ping-Ping; Zhang, Ning

    2016-05-01

    Nano-composite electrodeposition can improve the organizational structure of composite coatings and significantly improve the quality of the coating. Metal-ceramic composite coatings have improved mechanical, chemical and oxidation resistance properties, such as corrosion resistance, abrasion resistance and heat resistance. Content and distribution of codeposited particles determine the quality and performance of the coating. The factors which influenced the amount and distribution of codeposited particles were reviewed. The amount and distribution of codeposited particles are influenced by many process parameters, such as electrolyte composition and operating parameters. Finally an insight of the coming efforts to develop metal-ceramic composite coating is provided. It is the focus of future research to resolve reunion nanoparticles and improve codeposition amount and uniformly distributed nanoparticles of the coating.

  9. Experimental skin deposition of chromium on the hands following handling of samples of leather and metal.

    PubMed

    Bregnbak, David; Thyssen, Jacob P; Jellesen, Morten S; Zachariae, Claus; Johansen, Jeanne D

    2016-08-01

    Chromium is an important skin sensitizer. Exposure to it has been regulated in cement, and recently in leather. Studies on the deposition of chromium ions on the skin as a result of handling different chromium-containing materials are sparse, but could improve the risk assessment of contact sensitization and allergic contact dermatitis caused by chromium. To determine whether the handling of chromium-containing samples of leather and metal results in the deposition of chromium onto the skin. Five healthy volunteers participated. For 30 min, they handled samples of leather and metal known to contain and release chromium. Skin deposition of chromium was assessed with the acid wipe sampling technique. Acid wipe sampling of the participants' fingers showed chromium deposition on the skin in all participants who had been exposed to leather (range 0.01-0.20 µg/cm(2) ) and in 3 of 5 participants after they had manually handled metal discs (range 0.02-0.04 µg/cm(2) ). We found that samples of leather and metal had the ability to deposit chromium on the skin at significant levels, in spite of a short duration of exposure. © 2016 John Wiley & Sons A/S. Published by John Wiley & Sons Ltd.

  10. Metal abundances in the cool cores of galaxy clusters

    NASA Astrophysics Data System (ADS)

    de Grandi, S.; Molendi, S.

    2009-12-01

    We use XMM-Newton data to carry out a detailed study of the Si, Fe and Ni abundances in the cool cores of a representative sample of 26 local clusters. We performed a careful evaluation of the systematic uncertainties related to the instruments, the plasma codes and the spectral modeling, finding that the major source of uncertainty is the plasma codes. Our Si, Fe, Ni, Si/Fe and Ni/Fe distributions feature only moderate spreads (from 20% to 30%) around their mean values strongly suggesting similar enrichment processes at work in all our cluster cores. Our sample-averaged Si/Fe ratio is comparable to those measured in samples of groups and high luminosity ellipticals, implying that the enrichment process in ellipticals, dominant galaxies in groups and BCGs in clusters is quite similar. Although our Si/Fe and Ni/Fe abundance ratios are fairly well constrained, the large uncertainties in the supernova yields prevent us from making a firm assessment of the relative contribution of type Ia and core-collapsed supernovae to the enrichment process. All that can be said with some certainty is that both contribute to the enrichment of cluster cores. Tables and Appendix are only available in electronic form at http://www.aanda.org

  11. Spherical Clusters of Simple Metals: Madelung Energies and Structure.

    DTIC Science & Technology

    1986-06-01

    crystalline structures remain lower than those of the optimal structures even at cluster sizes of more than 90 atoms. Also the calculations of the...differ from crystalline structures up to clus- ter sizes of hundreds of atoms. Acknowledgements - The author would like to thank N.W. Ashcroft, J.W

  12. Multi-orbital cluster perturbation theory for transition metal oxides.

    PubMed

    Manghi, F

    2014-01-08

    We present an extension of cluster perturbation theory to include many-body correlations associated with local e-e repulsion in real materials. We show that this approach can describe the physics of complex correlated materials where different atomic species and different orbitals coexist. The prototypical case of MnO is considered.

  13. Adherence of ion beam sputter deposited metal films on H-13 steel

    NASA Technical Reports Server (NTRS)

    Mirtich, M. J.

    1980-01-01

    An electron bombardment argon ion source was used to sputter deposit 17 different metal and metal oxide films ranging in thickness from 1 to 8 micrometers on H-13 steel substrates. The film adherence to the substrate surface was measured using a tensile test apparatus. Comparisons in bond strength were made between ion beam, ion plating, and RF deposited films. A protective coating to prevent heat checking in H-13 steel dies used for aluminum die casting was studied. The results of exposing the coated substrates to temperatures up to 700 degrees are presented.

  14. Metal organic chemical vapor deposition of phase change Ge1Sb2Te4 nanowires.

    PubMed

    Longo, Massimo; Fallica, Roberto; Wiemer, Claudia; Salicio, Olivier; Fanciulli, Marco; Rotunno, Enzo; Lazzarini, Laura

    2012-03-14

    The self-assembly of Ge(1)Sb(2)Te(4) nanowires (NWs) for phase change memories application was achieved by metal organic chemical vapor deposition, catalyzed by Au nanoislands in a narrow range of temperatures and deposition pressures. In the optimized conditions of 400 °C, 50 mbar, the NWs are Ge(1)Sb(2)Te(4) single hexagonal crystals. Phase change memory switching was reversibly induced by nanosecond current pulses through metal-contacted NWs with threshold voltage of about 1.35 V.

  15. Steering-Enhanced Roughening during Metal Deposition at Grazing Incidence

    NASA Astrophysics Data System (ADS)

    van Dijken, Sebastiaan; Jorritsma, Louis C.; Poelsema, Bene

    1999-05-01

    It is shown that steering may have an important influence on the morphology of growing films. Steering originates from long-range attractive forces between incoming atoms and substrate atoms and leads to preferential arrival of atoms on top of islands. This phenomenon is most pronounced for grazing incidence deposition and results in significantly increased roughness of the growing film. Steering, which is expected to be generally valid but has so far been disregarded in growth studies, is illustrated for the growth of Cu/Cu(001).

  16. Radial metal abundance profiles in the intra-cluster medium of cool-core galaxy clusters, groups, and ellipticals

    NASA Astrophysics Data System (ADS)

    Mernier, F.; de Plaa, J.; Kaastra, J. S.; Zhang, Y.-Y.; Akamatsu, H.; Gu, L.; Kosec, P.; Mao, J.; Pinto, C.; Reiprich, T. H.; Sanders, J. S.; Simionescu, A.; Werner, N.

    2017-07-01

    The hot intra-cluster medium (ICM) permeating galaxy clusters and groups is not pristine, as it has been continuously enriched by metals synthesised in Type Ia (SNIa) and core-collapse (SNcc) supernovae since the major epoch of star formation (z ≃ 2-3). The cluster/group enrichment history and mechanisms responsible for releasing and mixing the metals can be probed via the radial distribution of SNIa and SNcc products within the ICM. In this paper, we use deep XMM-Newton/EPIC observations from a sample of 44 nearby cool-core galaxy clusters, groups, and ellipticals (CHEERS) to constrain the average radial O, Mg, Si, S, Ar, Ca, Fe, and Ni abundance profiles. The radial distributions of all these elements, averaged over a large sample for the first time, represent the best constrained profiles available currently. Specific attention is devoted to a proper modelling of the EPIC spectral components, and to other systematic uncertainties that may affect our results. We find an overall decrease of the Fe abundance with radius out to 0.9 r500 and 0.6 r500 for clusters and groups, respectively, in good agreement with predictions from the most recent hydrodynamical simulations. The average radial profiles of all the other elements (X) are also centrally peaked and, when rescaled to their average central X/Fe ratios, follow well the Fe profile out to at least 0.5 r500. As predicted by recent simulations, we find that the relative contribution of SNIa (SNcc) to the total ICM enrichment is consistent with being uniform at all radii, both for clusters and groups using two sets of SNIa and SNcc yield models that reproduce the X/Fe abundance pattern in the core well. In addition to implying that the central metal peak is balanced between SNIa and SNcc, our results suggest that the enriching SNIa and SNcc products must share the same origin and that the delay between the bulk of the SNIa and SNcc explosions must be shorter than the timescale necessary to diffuse out the metals

  17. Surface glass transition temperature characterized by metal-atom deposition/desorption on organic films

    NASA Astrophysics Data System (ADS)

    Tsujioka, Tsuyoshi; Okuda, Masaki

    2017-12-01

    Surfaces and interfaces play an important role in obtaining high-performance organic devices. An essential property of organic films is the surface glass transition temperature (surface-Tg) and many methods for characterizing surface-Tg have been studied. We propose a novel method for characterizing surface-Tg based on metal-vapor atom deposition and desorption. We monitored metal-vapor deposition and desorption on organic surfaces using double quartz crystal microbalances. Mg vapor is not deposited on organic surfaces with a low bulk-Tg such as a colorless photochromic diarylethene (DAE) film. This deposition phenomenon is caused by Mg-atom desorption from the surface based on active surface molecular motion. However, Mg deposition began after a certain time of continuous evaporation (deposition-threshold time). The threshold time elongated with increased substrate temperature and elongated dramatically at a substrate temperature several degrees below the bulk-Tg for DAE. The surface molecular motion becomes active and the metal-atom desorption accelerates as the temperature neared the surface-Tg. Thus a temperature with a dramatic elongation of the threshold time indicates the surface-Tg. This method can be applied to a variety of organic films.

  18. Adherence of ion beam sputter deposited metal films on H-13 steel

    NASA Technical Reports Server (NTRS)

    Mirtich, M. J.

    1980-01-01

    An electron bombardment argon ion source sputter deposited 17 metals and metal oxides on H-13 steel. The films ranged 1 to 8 micrometers in thickness and their adherence was generally greater than the capacity of the measuring device; adherence quality depended on proper precleaning of the substrate before deposition. N2 or air was introduced for correct stoichiometry in metallic compounds. Au, Ag, MgO, and Ta5Si3 films 8 microns thick have bond strength equal to 1 micron coatings; the bond strength of pure metallic films up to 5 microns thick was greater than the epoxy to film bond (8000 psi). The results of exposures of coated material to temperatures up to 700 C are presented.

  19. Mineral Deposit Data for Epigenetic Base- and Precious-metal and Uranium-thorium Deposits in South-central and Southwestern Montana and Southern and Central Idaho

    USGS Publications Warehouse

    Klein, T.L.

    2004-01-01

    Metal deposits spatially associated with the Cretaceous Boulder and Idaho batholiths of southwestern Montana and southern and central Idaho have been exploited since the early 1860s. Au was first discovered in placer deposits; exploitation of vein deposits in bedrock soon followed. In 1865, high-grade Ag vein deposits were discovered and remained economically important until the 1890s. Early high-grade deposits of Au, Ag and Pb were found in the weathered portions of the veins systems. As mining progressed to deeper levels, Ag and Pb grades diminished. Exploration for and development of these vein deposits in this area have continued until the present. A majority of these base- and precious-metal vein deposits are classified as polymetallic veins (PMV) and polymetallic carbonate-replacement (PMR) deposits in this compilation. Porphyry Cu and Mo, epithermal (Au, Ag, Hg and Sb), base- and precious-metal and W skarn, W vein, and U and Th vein deposits are also common in this area. The world-class Butte Cu porphyry and the Butte high-sulfidation Cu vein deposits are in this study area. PMV and PMR deposits are the most numerous in the region and constitute about 85% of the deposit records compiled. Several types of syngenetic/diagenetic sulfide mineral deposits in rocks of the Belt Supergroup or their equivalents are common in the region and they have been the source of a substantial metal production over the last century. These syngenetic deposits and their metamorphosed/structurally remobilized equivalents were not included in this database; therefore, deposits in the Idaho portion of the Coeur d'Alene district and the Idaho Cobalt belt, for example, have not been included because many of them are believed to be of this type.

  20. Intrinsic magnetic properties of bimetallic nanoparticles elaborated by cluster beam deposition.

    PubMed

    Dupuis, V; Khadra, G; Hillion, A; Tamion, A; Tuaillon-Combes, J; Bardotti, L; Tournus, F

    2015-11-14

    In this paper, we present some specific chemical and magnetic order obtained very recently on characteristic bimetallic nanoalloys prepared by mass-selected Low Energy Cluster Beam Deposition (LECBD). We study how the competition between d-atom hybridization, complex structure, morphology and chemical affinity affects their intrinsic magnetic properties at the nanoscale. The structural and magnetic properties of these nanoalloys were investigated using various experimental techniques that include High Resolution Transmission Electron Microscopy (HRTEM), Superconducting Quantum Interference Device (SQUID) magnetometry, as well as synchrotron techniques such as Extended X-ray Absorption Fine Structure (EXAFS) and X-ray Magnetic Circular Dichroism (XMCD). Depending on the chemical nature of the nanoalloys we observe different magnetic responses compared to their bulk counterparts. In particular, we show how specific relaxation in nanoalloys impacts their magnetic anisotropy; and how finite size effects (size reduction) inversely enhance their magnetic moment.