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Sample records for coinage metal surfaces

  1. Aromatic molecules on low-index coinage metal surfaces: Many-body dispersion effects

    NASA Astrophysics Data System (ADS)

    Jiang, Yingda; Yang, Sha; Li, Shuang; Liu, Wei

    2016-12-01

    Understanding the binding mechanism for aromatic molecules on transition-metal surfaces in atomic scale is a major challenge in designing functional interfaces for to (opto)electronic devices. Here, we employ the state-of-the-art many-body dispersion (MBD) approach, coupled with density functional theory methods, to study the interactions of benzene with low-index coinage metal surfaces. The many-body effects contribute mostly to the (111) surface, and leastly to the (110) surface. This corresponds to the same sequence of planar atomic density of face-centered-cubic lattices, i.e., (111) > (100) > (110). The binding energy for benzene/Au(110) is even stronger than that for benzene/Ag(110), due to a larger broadening of molecular orbitals in the former case. On the other hand, our calculations show almost identical binding energies for benzene on Ag(111) and Au(111), which contradicts the classic d-band center theory that could well predict the trend in chemisorption energies for various small molecules on a number of metal surfaces. Our results provide important insight into the benchmark adsorption systems with opener surfaces, which could help in designing more complex functional interfaces.

  2. Aromatic molecules on low-index coinage metal surfaces: Many-body dispersion effects

    PubMed Central

    Jiang, Yingda; Yang, Sha; Li, Shuang; Liu, Wei

    2016-01-01

    Understanding the binding mechanism for aromatic molecules on transition-metal surfaces in atomic scale is a major challenge in designing functional interfaces for to (opto)electronic devices. Here, we employ the state-of-the-art many-body dispersion (MBD) approach, coupled with density functional theory methods, to study the interactions of benzene with low-index coinage metal surfaces. The many-body effects contribute mostly to the (111) surface, and leastly to the (110) surface. This corresponds to the same sequence of planar atomic density of face-centered-cubic lattices, i.e., (111) > (100) > (110). The binding energy for benzene/Au(110) is even stronger than that for benzene/Ag(110), due to a larger broadening of molecular orbitals in the former case. On the other hand, our calculations show almost identical binding energies for benzene on Ag(111) and Au(111), which contradicts the classic d-band center theory that could well predict the trend in chemisorption energies for various small molecules on a number of metal surfaces. Our results provide important insight into the benchmark adsorption systems with opener surfaces, which could help in designing more complex functional interfaces. PMID:28004793

  3. Coinage Metal Hydrides: Synthesis, Characterization, and Reactivity.

    PubMed

    Jordan, Abraham J; Lalic, Gojko; Sadighi, Joseph P

    2016-08-10

    Hydride complexes of copper, silver, and gold encompass a broad array of structures, and their distinctive reactivity has enabled dramatic recent advances in synthesis and catalysis. This Review summarizes the synthesis, characterization, and key stoichiometric reactions of isolable or observable coinage metal hydrides. It discusses catalytic processes in which coinage metal hydrides are known or probable intermediates, and presents mechanistic studies of selected catalytic reactions. The purpose of this Review is to convey how developments in coinage metal hydride chemistry have led to new organic transformations, and how developments in catalysis have in turn inspired the synthesis of reactive new complexes.

  4. Graphene growth on coinage-metal substrates

    NASA Astrophysics Data System (ADS)

    McCarty, Kevin

    2012-02-01

    The low solubility of carbon in Cu and Au gives these coinage metals advantages as substrates for graphene growth. Namely, growth occurs exclusively by surface processes, avoiding the complications of C segregating from the bulk of the metal substrate. However, the relatively weak interactions of Cu and Au with graphene can lead to mosaic films having large ranges of in-plane orientations. This talk will emphasize understanding the relationship between the microstructure of graphene sheets and the mechanisms of island nucleation and growth. We use low-energy electron microscopy (LEEM) to observe growth. We find that bunches of substrate steps on Cu(111) can generate misorientation boundaries in a graphene sheet as it overgrows the steps [1]. Thus, growth on rough Cu(111) leads to large rotational disorder. Optimized growth on smooth Cu(111) and Au(111), however, produces islands all in close registry to a single in-plane orientation. On Cu(100), the most abundant grain orientation of commercial Cu foils, graphene islands align around two equivalent in-plane Cu directions [2]. This inherent source of disorder from symmetry mismatch is further compounded by large spreads of orientation around the equivalent directions. The substrate choice also affects the microscopic growth mechanism. The rate that C diffuses to the graphene islands limits growth on Cu(111) [and likely on Au(111)]. The sheet edges are then morphologically unstable, with dendritic islands at low temperature and six-fold loped islands at higher temperature. In contrast, growth on Cu(100) is limited by the rate of C attaching to the graphene edge. This mechanism, combined with the symmetry mismatch, produces two-fold islands. Finally, the coinage metals will be compared to other transition metal substrates. [4pt] [1] Phys. Rev. B 84, p. 155425 (2011). [0pt] [2] Nano Lett. 10, p. 4890 (2010).

  5. Adsorption of precious and coinage metals on Rh (111), Ru (0001) and W (110) surfaces

    NASA Astrophysics Data System (ADS)

    Zhu, Quanxi; Wang, Shao-qing

    2017-07-01

    Bimetallic surface alloys have been considered as an effective strategy to achieve better catalytic performance and to modify the work function of the substrate toward metal-gate electrode application. We perform a systematical investigation of Group 10 and Group 11 transition metals adsorption on Rh (111), Ru (0001) and W (110) surfaces with various coverages using first-principles method. Through comparing the Bader charge results and the plots of work function shift, it is found that the polarization effect plays an important role in modification of the bimetallic surface work functions rather than the charge transfer effect especially at low coverages. The coverage-dependent work function behavior gives a general feature: as it has a large negative shift at 0.25ML coverage, then increases almost linearly with the coverage and followed by a saturation value which is controlled by the lattice strain. It is also found that the metal over-layer growth modes are correlated with the specific features of the coverage-dependent metal-substrate adhesion energy. All these findings may give some guidelines for the bimetallic catalysts design in terms of growth, stability and activity.

  6. Photon-driven charge transfer and Herzberg-Teller vibronic coupling mechanism in surface-enhanced Raman scattering of p-aminothiophenol adsorbed on coinage metal surfaces: a density functional theory study.

    PubMed

    Zhao, Liu-Bin; Huang, Rong; Huang, Yi-Fan; Wu, De-Yin; Ren, Bin; Tian, Zhong-Qun

    2011-10-07

    The chemical enhancement effects in surface-enhanced Raman scattering of p-aminothiophenol (PATP, it is also called p-mercaptoaniline or p-aminobenzenthiol) adsorbed on coinage metal surfaces with single thiol end or trapped into metal-molecule-metal junctions with both thiol and amino groups have been studied by density functional theory (DFT). We focus on the influence of photon-driven charge transfer (PDCT) and chemical bonding interaction (ground-state charge transfer) on the intensity enhancement and frequency shift in the surface Raman spectra of PATP. For comparison, the electronic structures and transitions of free PATP are studied first. The simulated pre-resonance UV Raman spectra illustrate that b(2) modes can be selectively enhanced via vibronic coupling. The fundamentals of all the b(2) modes in the frequency range of 1000 to 1650 cm(-1) are assigned in detail. For PATP adsorbed on coinage metals, the time-dependent-DFT calculations indicate that the low-lying CT excited state arises from the π bonding orbital of molecule to the antibonding s orbital of metallic clusters. Our results further show that the PDCT resonance-like Raman scattering mechanism enhances the totally symmetric vibrational modes and the NH(2) wagging vibration. Finally, the effect of chemical bonding interaction is also investigated. The amino group binding to metals gives a characteristic band of the NH(2) wagging mode with the large blueshift frequency and an intense Raman signal. © 2011 American Institute of Physics

  7. Photon-driven charge transfer and Herzberg-Teller vibronic coupling mechanism in surface-enhanced Raman scattering of p-aminothiophenol adsorbed on coinage metal surfaces: A density functional theory study

    NASA Astrophysics Data System (ADS)

    Zhao, Liu-Bin; Huang, Rong; Huang, Yi-Fan; Wu, De-Yin; Ren, Bin; Tian, Zhong-Qun

    2011-10-01

    The chemical enhancement effects in surface-enhanced Raman scattering of p-aminothiophenol (PATP, it is also called p-mercaptoaniline or p-aminobenzenthiol) adsorbed on coinage metal surfaces with single thiol end or trapped into metal-molecule-metal junctions with both thiol and amino groups have been studied by density functional theory (DFT). We focus on the influence of photon-driven charge transfer (PDCT) and chemical bonding interaction (ground-state charge transfer) on the intensity enhancement and frequency shift in the surface Raman spectra of PATP. For comparison, the electronic structures and transitions of free PATP are studied first. The simulated pre-resonance UV Raman spectra illustrate that b2 modes can be selectively enhanced via vibronic coupling. The fundamentals of all the b2 modes in the frequency range of 1000 to 1650 cm-1 are assigned in detail. For PATP adsorbed on coinage metals, the time-dependent-DFT calculations indicate that the low-lying CT excited state arises from the π bonding orbital of molecule to the antibonding s orbital of metallic clusters. Our results further show that the PDCT resonance-like Raman scattering mechanism enhances the totally symmetric vibrational modes and the NH2 wagging vibration. Finally, the effect of chemical bonding interaction is also investigated. The amino group binding to metals gives a characteristic band of the NH2 wagging mode with the large blueshift frequency and an intense Raman signal.

  8. Special Issue: Coinage Metal (Copper, Silver, and Gold) Catalysis.

    PubMed

    Carabineiro, Sónia Alexandra Correia

    2016-06-08

    The subject of catalysis by coinage metals (copper, silver, and gold) comes up increasingly day-by-day. This Special Issue aims to cover the numerous aspects of the use of these metals as catalysts for several reactions. It deals with synthesis and characterization of copper, silver and gold based catalysis, their characterization and use, both for heterogeneous and homogeneous catalysis, and some of their potential applications.

  9. Theoretical study of the adsorption of benzene on coinage metals

    PubMed Central

    Reckien, Werner; Eggers, Melanie

    2014-01-01

    Summary The adsorption of benzene on the M(111), M(100) and M(110) surfaces of the coinage metals copper (M = Cu), silver (M = Ag) and gold (M = Au) is studied on the basis of density functional theory (DFT) calculations with an empirical dispersion correction (D3). Variants of the Perdew–Burke–Ernzerhof functionals (PBE, RPBE and RevPBE) in combination with different versions of the dispersion correction (D3 and D3(BJ)) are compared. PBE-D3, PBE-D3(BJ) and RPBE-D3 give similar results which exhibit a good agreement with experimental data. RevPBE-D3 and RevPBE-D3(BJ) tend to overestimate adsorption energies. The inclusion of three-center terms (PBE-D3(ABC)) leads to a slightly better agreement with the experiment in most cases. Vertical adsorbate–substrate distances are calculated and compared to previous theoretical results. The observed trends for the surfaces and metals are consistent with the calculated adsorption energies. PMID:25161736

  10. Metal-organic interface functionalization via acceptor end groups: PTCDI on coinage metals

    NASA Astrophysics Data System (ADS)

    Franco-Cañellas, Antoni; Wang, Qi; Broch, Katharina; Duncan, David A.; Thakur, Pardeep Kumar; Liu, Lijia; Kera, Satoshi; Gerlach, Alexander; Duhm, Steffen; Schreiber, Frank

    2017-06-01

    We present a comprehensive study of the complex interface between perylene-3,4,9,10-tetracarboxylic diimide (PTCDI) and the (111) surfaces of the three coinage metals. The specific structural, electronic, and chemical properties of the interface rendered by the different substrate reactivities are monitored with low-energy electron diffraction (LEED), x-ray standing waves (XSW), and ultraviolet and x-ray photelectron spectroscopy (UPS and XPS). In particular, the balance between molecule-substrate and molecule-molecule interactions is considered when interpreting the core-level spectra of the different interfaces. By presenting additional adsorption distances of the unsubstituted perylene, we show that the molecular functionalization via end groups with acceptor character facilitates the charge transfer from the substrate but it is not directly responsible for the associated short adsorption distances, demonstrating that this frequently assumed correlation is not necessarily correct.

  11. The chemical origin and catalytic activity of coinage metals: from oxidation to dehydrogenation.

    PubMed

    Syu, Cih-Ying; Yang, Hao-Wen; Hsu, Fu-Hsing; Wang, Jeng-Han

    2014-04-28

    The high oxidation activity of coinage metals (Cu, Ag and Au) has been widely applied in various important reactions, such as oxidation of carbon monoxide, alkenes or alcohols. The catalytic behavior of those inert metals has mostly been attributable to their size effect, the physical effect. In the present study, the chemical effects on their high oxidation activity have been investigated. We mechanistically examine the direct and oxidative dehydrogenation (partial oxidation) reactions of ethanol to acetaldehyde on a series of transition metals (groups 9, 10 and 11) with identical physical characteristics and varied chemical origins using density functional theory (DFT) calculations and electronic structure analyses at the GGA-PW91 level. The energetic results show that coinage metals have much lower activation energies and higher exothermicities for the oxidative dehydrogenation steps although they have higher energy for the direct dehydrogenation reaction. In the electronic structure analyses, coinage metals with saturated d bands can efficiently donate electrons to O* and OH*, or other electronegative adspecies, and better promote their p bands to higher energy levels. The negatively charged O* and OH* with high-lying p bands are responsible for lowering the energies in oxidative steps. The mechanistic understanding well explains the better oxidation activity of coinage metals and provides valuable information on their utilization in other useful applications, for example, the dehydrogenation process.

  12. Resistance to sulfur poisoning of Ni-based alloy with coinage (IB) metals

    NASA Astrophysics Data System (ADS)

    Xu, Xiaopei; Zhang, Yanxing; Yang, Zongxian

    2015-12-01

    The poisoning effects of S atom on the (1 0 0), (1 1 0) and (1 1 1) metal surfaces of pure Ni and Ni-based alloy with IB (coinage) metals (Cu, Ag, Au) are systematically studied. The effects of IB metal dopants on the S poisoning features are analyzed combining the density functional theory (DFT) results with thermodynamics data using the ab initio atomistic thermodynamic method. It is found that introducing IB doping metals into Ni surface can shift the d-band center downward from the Fermi level and weaken the adsorption of S on the (1 0 0) and (1 1 0) surfaces, and the S tolerance ability increases in the order of Ni, Cu/Ni, Ag/Ni and Au/Ni. Nevertheless, on the (1 1 1) surface, the S tolerance ability increases in the order of Ag/Ni (or Cu/Ni), Ni, and Au/Ni. When we increase the coverage of the IB metal dopants, we found that not only Au, but Cu and Ag can increase its S tolerance. We therefore propose that alloying can increase its S tolerance and alloying with Au would be a better way to increase the resistance to sulfur poisoning of the Ni anode as compared with the pure Ni and the Ag- or, Cu-doped Ni materials.

  13. Surface acidity scales: Experimental measurements of Brønsted acidities on anatase TiO2 and comparison with coinage metal surfaces

    NASA Astrophysics Data System (ADS)

    Silbaugh, Trent L.; Boaventura, Jaime S.; Barteau, Mark A.

    2016-08-01

    The first quantitative surface acidity scale for Brønsted acids on a solid surface is presented through the use of titration-displacement and equilibrium experiments on anatase TiO2. Surface acidities of species on TiO2 correlated with gas phase acidities, as was previously observed in qualitative studies of Brønsted acid displacement on Ag(110), Cu(110) and Au(111). A 90% compression of the surface acidity scale relative to the gas phase was observed due to compensation from the covalent component of the conjugate base - surface bond. Adsorbed conjugate bases need not be completely anionic for correlations with gas phase acidities to hold. Positive and negative substituent effects, such as substituted fluorine and hydrocarbon sidechain dispersion interactions with the surface, may modify the surface acidity scale, in agreement with previous experimental and theoretical work on Au(111).

  14. Recent Developments in Coinage Metal Catalyzed Transformations of Stabilized Vinyldiazo Compounds: Beyond Carbenic Pathways.

    PubMed

    López, Enol; González-Pelayo, Silvia; López, Luis A

    2017-03-01

    Transition metal-catalyzed transformations of vinyldiazo compounds have become a versatile tool in organic synthesis. Although several transition metals have been investigated for this purpose, this field has been mainly dominated by dirhodium catalysts. Remarkable levels of chemo-, regio-, diastereo- and enantioselectivity have been reached in some of these rhodium-catalyzed transformations. In the last few years coinage metals have also emerged as useful catalysts in transformations involving vinyldiazo compounds. In some cases, highly efficient catalyst-dependent protocols arising from divergent mechanistic pathways have been reported. In this Personal Account, we aim to showcase recent advances in metal coinage catalyzed transformations of vinyldiazoacetates, an exciting field of research to which our group has actively contributed in the last few years.

  15. Sonochemical procedures; the main synthetic method for synthesis of coinage metal ion supramolecular polymer nano structures.

    PubMed

    Shahangi Shirazi, Fatemeh; Akhbari, Kamran

    2016-07-01

    During the last two decades, supramolecular polymers have received great attention and the number of their synthesized compounds is still growing. Although people have long been interested in their crystalline network form it was only until 2005 that the first examples of nano- or microscale coordination polymers particles be demonstrated. This review tries to give an overview of all nano supramolecular compounds which were reported from coinage metal ions, their attributed synthetic procedures and to investigate the relation between the dimensions of coinage metal ions (Cu, Ag and Au) coordination and supramolecular polymers with their nano-structural morphologies and dimensions. Eleven compounds (from twenty compounds) with nano-structure morphology were prepared by sonochemical process and Ag(I) coordination and supramolecular polymer nano-structures can be easily prepared by sonochemical procedures.

  16. Lone pair interactions with coinage metal atoms: Weak van der Waals complexes of the coinage metal atoms with water and ammonia

    NASA Astrophysics Data System (ADS)

    Antušek, Andrej; Urban, Miroslav; Sadlej, Andrzej J.

    2003-10-01

    Interaction energies between the coinage metal atoms (Cu, Ag, and Au) and lone-pair donating molecules (H2O and NH3) are calculated by the spin adapted restricted open-shell Hartree-Fock coupled cluster method with the scalar relativistic effects accounted for by the Douglas-Kroll approximation. All ammonia complexes CuNH3, AgNH3, and AuNH3 are found to be of C3v symmetry with the counterpoise corrected interaction energies equal to -16.68, -6.87, and -14.64 mH for Cu, Ag, and Au, respectively. In the case of the water molecule the complexes are much weaker with the counterpoise corrected interaction energies equal to -3.78, -1.81, and -1.77 mH, for the three metal atoms, respectively. Moreover, all complexes with the water molecule are nonplanar. For both lone-pair donating molecules the structure and energetics of their complexes with the coinage metal atoms is mostly due to electron correlation effects. The relativistic effects are found to increase the bonding energies in the series of the ammonia complexes, whereas they reduce the bonding energy in the AgOH2 complex and are essentially negligible for CuOH2 and AuOH2. The calculated complex geometries and interaction energies are discussed in terms of different models. The pattern of interaction energies is discussed in terms of the balance between long-range induction and dispersion contributions and short-range forces. Also the possibility of some charge transfer from the lone-pair donor to the metal atom is considered and supported by analysis of the ionization potential and electron affinity data. The relativistic reduction of the size of the coinage metal atoms is found to be of importance as well. The calculated structural data are used to interpret the experimental observation concerning the existence of well resolved resonantly enhanced multiphoton ionization (REMPI) spectra of the ammonia-silver complexes and the absence of the corresponding spectra of the water-silver complex. This experimental

  17. Surface topology investigation for ancient coinage assessment using optical interferometry

    NASA Astrophysics Data System (ADS)

    Grynszpan, R. I.; Pastol, J. L.; Lesko, S.; Paris, E.; Raepsaet, C.

    In order to demonstrate the capabilities of white-light interferometry depth profiling (WLI-DP) for ancient coinage assessment, we investigated a series of notorious 1786 gold coins, bearing Louis XVI's `horned' effigy, and allegedly minted in Strasbourg. Scanning electron microscopy as well as WLI-DP observations unambiguously indicate that both previously differentiated `single'- and `double'-horned varieties originated from a unique minting tool. Moreover, from topological measurements, we infer that `single-horned' coins, rather than wearing out into `double-horned' coins, proceeded from the latter variety during minting by progressive failure of an already altered die. Whereas present observations do not exclude initial forgery, they suggest that protrusions resulted from progressive incidental in-service die deterioration.

  18. Widely applicable coinage metal window electrodes on flexible polyester substrates applied to organic photovoltaics.

    PubMed

    Stec, Helena M; Hatton, Ross A

    2012-11-01

    The fabrication, exceptional properties, and application of 8 nm thick Cu, Ag, Au, and Cu/Ag bilayer electrodes on flexible polyethylene terephthalate (PET) and polyethylene naphthalate (PEN) substrates is reported. These electrodes are fabricated using a solvent free process in which the plastic surface is chemically modified with a molecular monolayer of thiol and amine terminated alkylsilanes prior to metal deposition. The resulting electrodes have a sheet resistance of ≤14 Ω sq⁻¹, are exceptionally robust and can be rapidly thermally annealed at 200 °C to reduce their sheet resistance to ≤9 Ω sq⁻¹. Notably, annealing Au electrodes briefly at 200 °C causes the surface to revert almost entirely to the {111} face, rendering it ideal as a model electrode for fundamental science and practical application alike. The power conversion efficiency of 1 cm² organic photovoltaics (OPVs) employing 8 nm Ag and Au films as the hole-extracting window electrode exhibit performance comparable to those on indium-tin oxide, with the advantage that they are resistant to repeated bending through a small radius of curvature and are chemically well-defined. OPVs employing Cu and bilayer Cu:Ag electrodes exhibit inferior performance due to a lower open-circuit voltage and fill factor. Measurements of the interfacial energetics made using the Kelvin probe technique provide insight into the physical reason for this difference. The results show how coinage metal electrodes offer a viable alternative to ITO on flexible substrates for OPVs and highlight the challenges associated with the use of Cu as an electrode material in this context.

  19. Unusual hydrogen bonding behavior in binary complexes of coinage metal anions with water

    NASA Astrophysics Data System (ADS)

    Schneider, Holger; Boese, A. Daniel; Weber, J. Mathias

    2005-08-01

    We have studied the interaction of atomic coinage metal anions with water molecules by infrared photodissociation spectroscopy of M-•H2O•Arn clusters (M =Cu, Ag, Au; n =1, 2). We compare our observations with calculations on density-functional and coupled cluster levels of theory. The gold anion is bound to the water molecule by a single ionic hydrogen bond, similar to the halide-water complexes. In contrast, zero-point motion in the silver and copper complexes leads to a deviation from this motif.

  20. 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.

  1. Adsorption of large hydrocarbons on coinage metals: a van der Waals density functional study.

    PubMed

    Björk, Jonas; Stafström, Sven

    2014-09-15

    The adsorption of organic molecules onto the close-packed facets of coinage metals is studied, and how accurately adsorption heights can be described by using recent advances of the van der Waals density functional (vdWDF), with optPBE/vdWDF, optB86b/vdWDF, vdWDF2, and rev/vdWDF2 functionals is illustrated. The adsorption of two prototypical aromatic hydrocarbons is investigated, and the calculated adsorption heights are compared to experimental literature values from normal incident X-ray standing wave absorption and a state-of-the-art semi-empirical method. It is shown that both the optB86b/vdWDF and rev/vdWDF2 functionals describe adsorption heights with an accuracy of 0.1 Å, compared to experimental values, and are concluded as reliable methods of choice for related systems.

  2. Adsorption of methylene blue and its N-demethylated derivatives on the (111) face of coinage metals: The importance of dispersion interactions

    NASA Astrophysics Data System (ADS)

    Zhou, Linsen; Johnson, Ryan; Habteyes, Terefe; Guo, Hua

    2017-04-01

    The adsorption of methylene blue and its N-demethylated derivatives on the (111) surface of three coinage metals is investigated using density functional theory with and without the inclusion of dispersion interactions. It is shown that the adsorption of these dye molecules on the metal surfaces can be largely classified as physisorption as the adsorption energy is dominated by dispersion interactions. While the molecules are found to adsorb on Au and Ag parallel to the surface with molecular geometries basically unaltered, the adsorption on Cu(111) features a butterfly configuration, accompanied by the largest adsorption energies among the three metal surfaces. The significant covalent character on Cu(111) is analyzed from the perspective of electronic structure.

  3. IRMPD Spectroscopy of Metalated Flavins: Structure and Bonding of Lumiflavin Complexes with Alkali and Coinage Metal Ions.

    PubMed

    Nieto, Pablo; Günther, Alan; Berden, Giel; Oomens, Jos; Dopfer, Otto

    2016-10-01

    Flavins are a fundamental class of biomolecules, whose photochemical properties strongly depend on their environment and their redox and metalation state. Infrared multiphoton dissociation (IRMPD) spectra of mass selected isolated metal-lumiflavin ionic complexes (M+LF) are analyzed in the fingerprint range (800-1830 cm-1) to determine the bonding of lumiflavin with alkali (M=Li, Na, K, Cs) and coinage (M=Cu, Ag) metal ions. The complexes are generated in an electrospray ionization source coupled to an ion cyclotron resonance mass spectrometer and the IR free electron laser FELIX. Vibrational and isomer assignments of the IRMPD spectra are accomplished by comparison to quantum chemical calculations at the B3LYP/cc-pVDZ level, yielding structure, binding energy, bonding mechanism, and spectral properties of the complexes. The most stable binding sites identified in the experiments involve metal bonding to the oxygen atoms of the two available CO groups of LF. Hence, CO stretching frequencies are a sensitive indicator of both the metal binding site and the metal bond strength. More than one isomer is observed for M=Li, Na, and K, and the preferred CO binding site changes with the size of the alkali ion. For Cs+LF only one isomer is identified although the energies of the two most stable structures differ by less than 7 kJ/mol. While the M+-LF bonds for alkali ions are mainly based on electrostatic forces, substantial covalent contributions lead to stronger bonds for the coinage metal ions. Comparison between lumiflavin and lumichrome reveals substantial differences in the metal binding motifs and interactions due to the different flavin structures.

  4. Coinage Metal Superatomic Cores: Insights into Their Intrinsic Stability and Optical Properties from Relativistic DFT Calculations.

    PubMed

    Gam, Franck; Paez-Hernandez, Dayan; Arratia-Perez, Ramiro; Liu, C W; Kahlal, Samia; Saillard, Jean-Yves; Muñoz-Castro, Alvaro

    2017-08-22

    Coinage-metal atomically precise nanoclusters are made of a well-defined metallic core embedded in a ligand-protecting outer shell. Whereas gold derivatives are particularly well documented, examples of silver nanoclusters are somewhat limited and copper species remain particularly scare. Our DFT relativistic calculations on superatomic metallic cores indicate that copper species are almost as stable as gold clusters and more stable than their silver counterparts. Thus, for silver superatomic cores, the role of the stabilizing ligands is more crucial in the stabilization of the overall structure, in comparison to copper and gold. Hence, the chemistry of the earlier counterparts of gold, especially copper, should grow quickly with at least characterizations of species related to that found in the heavier elements in the triad, which requires tackling synthetic challenges. Time-dependent (TD)-DFT calculations show that with an increase of the cluster core nuclearity, the absorption bands are redshifted, allowing us to differentiate between the clusters types. Moreover, the optical properties of the silver cores are fairly different from that of their Cu and Au relatives. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Fixed-charge phosphine ligands to explore gas-phase coinage metal-mediated decarboxylation reactions.

    PubMed

    Vikse, Krista; Khairallah, George N; McIndoe, J Scott; O'Hair, Richard A J

    2013-05-14

    A combination of multistage mass spectrometry experiments and density functional theory (DFT) calculations were used to examine the decarboxylation reactions of a series of metal carboxylate complexes bearing a fixed-charge phosphine ligand, [(O3SC6H4)(C6H5)2PM(I)O2CR](-) (M = Cu, Ag, Au; R = Me, Et, benzyl, Ph). Collision-induced dissociation (CID) of these complexes using an LTQ linear ion mass spectrometer results in three main classes of reactions being observed: (1) decarboxylation; (2) loss of the phosphine ligand; (3) loss of carboxylic acid. The gas-phase unimolecular chemistry of the resultant decarboxylated organometallic ions, [(O3SC6H4)(C6H5)2PM(I)R](-), were also explored using CID experiments, and fragment primarily via loss of the phosphine ligand. Energy-resolved CID experiments on [(O3SC6H4)(C6H5)2PM(I)O2CR](-) (M = Cu, Ag, Au; R = Me, Et, benzyl, Ph) using a Q-TOF mass spectrometer were performed to gain a more detailed understanding of the factors influencing coinage metal-catalyzed decarboxylation and DFT calculations on the major fragmentation pathways aided in interpretation of the experimental results. Key findings are that: (1) the energy required for loss of the phosphine ligand follows the order Ag < Cu < Au; (2) the ease of decarboxylation of the coordinated RCO2 groups follows the order of R: Ph < PhCH2 < Me < Et; (3) in general, copper is best at facilitating decarboxylation, followed by gold then silver. The one exception to this trend is when R = Ph and M = Au which has the highest overall propensity for decarboxylation. The influence of the phosphine ligand on decarboxylation is also considered in comparison with previous studies on metal carboxylates that do not contain a phosphine ligand.

  6. Coinage Metal Complexes of Bis-Alkynyl-Functionalized N-Heterocyclic Carbenes: Reactivity, Photophysical Properties, and Quantum Chemical Investigations.

    PubMed

    Kiefer, Claude; Bestgen, Sebastian; Gamer, Michael T; Kühn, Michael; Lebedkin, Sergei; Weigend, Florian; Kappes, Manfred M; Roesky, Peter W

    2017-01-31

    Bis-phenylpropynyl-functionalized imidazolium salts and their corresponding gold and copper N-heterocyclic carbene (NHC) complexes were prepared in order to investigate their potential application for the synthesis of heterometallic coinage metal compounds. By transmetalation reactions with different precious metal sources, including copper and silver phenylacetylides [MCCPh]n (M=Cu, Ag), polynuclear compounds were obtained, which were further investigated for their photoluminescence properties. Additionally, one gold NHC complex was post-functionalized by autocatalytic hydration of the alkynyl side chains. Time-dependent DFT investigations of singlet electronic excitations in representative complexes revealed excited states of diverse character, as determined by the specific complex structure and metallophilic interactions.

  7. Coinage metal exciplexes with helium atoms: a theoretical study of M*(2L)He(n) (M = Cu, Ag, Au; L = P,D).

    PubMed

    Cargnoni, Fausto; Ponti, Alessandro; Mella, Massimo

    2013-11-14

    The structure and energetics of exciplexes M*((2)L)He(n) (M = Cu, Ag and Au; L = P and D) in their vibrational ground state are studied by employing diffusion Monte Carlo (DMC). Interaction potentials between the excited coinage metals and He atoms are built using the Diatomics-in-Molecule (DIM) approach and ab initio potential curves for the M((2)L)-He dimers. Extending our previous work [Cargnoni et al., J. Phys. Chem. A, 2011, 115, 7141], we computed the dimer potential for Au in the (2)P and (2)D states, as well for Cu and Ag in the (2)D state, employing basis set superposition error-corrected Configuration Interaction calculations. We found that the (2)Π potential correlating with the (2)P state of Au is substantially less binding than for Ag and Cu, a trend well supported by the M(+) ionic radiuses. Conversely, the interaction potentials between a (n - 1)d(9)ns(2 2)D metal and He present a very weak dependency on M itself or the projection of the angular momentum along the dimer axis. This is due to the screening exerted by the ns(2) electrons on the hole in the (n - 1)d shell. Including the spin-orbit coupling perturbatively in the DIM energy matrix has a major effect on the lowest potential energy surface of the (2)P manifold, the one for Cu allowing the formation of a "belt" of five He atoms while the one for Au being completely repulsive. Conversely, spin-orbit coupling has only a weak effect on the (2)D manifold due to the nearly degenerate nature of the diatomic potentials. Structural and energetic results from DMC have been used to support experimental indications for the formation of metastable exciplexes or the opening of non-radiative depopulation channels in bulk and cold gaseous He.

  8. Molecular density functional calculations in the regular relativistic approximation: Method, application to coinage metal diatomics, hydrides, fluorides and chlorides, and comparison with first-order relativistic calculations

    NASA Astrophysics Data System (ADS)

    van Wüllen, Christoph

    1998-07-01

    The application of the zeroth-order regular relativistic approximation (ZORA) for molecular density functional calculations is investigated. By introducing a model potential to construct the kinetic energy operator, stationarity of the energy with respect to orbital variations is gained and most problems connected with gauge dependence of the regular approximation are eliminated. The formulation of a geometry gradient is greatly facilitated using this formalism. Calculations for the coinage metal hydrides (CuH, AgH, AuH) as well as for the homonuclear (Cu2, Ag2, Au2) and heteronuclear (CuAg, CuAu, AgAu) diatomics show that the results of ZORA calculations within the electrostatic shift approximation, as introduced by van Lenthe and co-workers, can be duplicated using the simpler scheme proposed in this work. Results for the coinage metal fluorides (CuF, AgF, AuF) and chlorides (CuCl, AgCl, AuCl) are presented as well. First-order relativistic calculations have been performed for all systems to assess the applicability of leading-order relativistic perturbation theory.

  9. Spin and orbital magnetism of coinage metal trimers (Cu{sub 3}, Ag{sub 3}, Au{sub 3}): A relativistic density functional theory study

    SciTech Connect

    Afshar, Mahdi; Sargolzaei, Mohsen

    2013-11-15

    We have demonstrated electronic structure and magnetic properties of Cu{sub 3}, Ag{sub 3} and Au{sub 3} trimers using a full potential local orbital method in the framework of relativistic density functional theory. We have also shown that the non-relativistic generalized gradient approximation for the exchange-correlation energy functional gives reliable magnetic properties in coinage metal trimers compared to experiment. In addition we have indicated that the spin-orbit coupling changes the structure and magnetic properties of gold trimer while the structure and magnetic properties of copper and silver trimers are marginally affected. A significant orbital moment of 0.21μ{sub B} was found for most stable geometry of the gold trimer whereas orbital magnetism is almost quenched in the copper and silver trimers.

  10. Spin and orbital magnetism of coinage metal trimers (Cu{sub 3}, Ag{sub 3}, Au{sub 3}): A relativistic density functional theory study

    SciTech Connect

    Afshar, Mahdi; Sargolzaei, Mohsen

    2013-11-15

    We have demonstrated electronic structure and magnetic properties of Cu{sub 3}, Ag{sub 3} and Au{sub 3} trimers using a full potential local orbital method in the framework of relativistic density functional theory. We have also shown that the non-relativistic generalized gradient approximation for the exchange-correlation energy functional gives reliable magnetic properties in coinage metal trimers compared to experiment. In addition we have indicated that the spin-orbit coupling changes the structure and magnetic properties of gold trimer while the structure and magnetic properties of copper and silver trimers are marginally affected. A significant orbital moment of 0.21μ{sub B} was found for most stable geometry of the gold trimer whereas orbital magnetism is almost quenched in the copper and silver trimers.

  11. N-Heterocyclic Carbene Coinage Metal Complexes of the Germanium-Rich Metalloid Clusters [Ge₉R₃](-) and [Ge₉R(I)₂]²(-) with R = Si((i)Pr)₃ and R(I) = Si(TMS)₃.

    PubMed

    Geitner, Felix S; Giebel, Michael A; Pöthig, Alexander; Fässler, Thomas F

    2017-07-19

    We report on the synthesis of novel coinage metal NHC (N-heterocyclic carbene) compounds of the germanium-rich metalloid clusters [Ge₉R₃](-) and [Ge₉R(I)₂]²(-) with R = Si((i)Pr)₃ and R(I) = Si(TMS)₃. NHC(Dipp)Cu{η³Ge₉R₃} with R = Si((i)Pr)₃ (1) represents a less bulky silyl group-substituted derivative of the known analogous compounds with R = Si((i)Bu)₃ or Si(TMS)₃. The coordination of the [NHC(Dipp)Cu]⁺ moiety to the cluster unit occurs via one triangular face of the tri-capped trigonal prismatic [Ge₉] cluster. Furthermore, a series of novel Zintl cluster coinage metal NHC compounds of the type (NHCM)₂{η³Ge₉R(I)₂} (R(I) = Si(TMS)₃ M = Cu, Ag and Au; NHC = NHC(Dipp) or NHC(Mes)) is presented. These novel compounds represent a new class of neutral dinuclear Zintl cluster coinage metal NHC compounds, which are obtained either by the stepwise reaction of a suspension of K12Ge17 with Si(TMS)₃Cl and the coinage metal carbene complexes NHCMCl (M = Cu, Ag, Au), or via a homogenous reaction using the preformed bis-silylated cluster K₂[Ge₉(Si(TMS)₃)₂] and the corresponding NHCMCl (M = Cu, Ag, Au) complex. The molecular structures of NHC(Dipp)Cu{η³Ge₉(Si((i)Pr)₃)₃} (1) and (NHC(Dipp)Cu)₂{η³-Ge₉(Si(TMS)₃)₂} (2) were determined by single crystal X-ray diffraction methods. In 2, the coordination of the [NHC(Dipp)Cu]⁺ moieties to the cluster unit takes place via both open triangular faces of the [Ge₉] entity. Furthermore, all compounds were characterized by means of NMR spectroscopy (¹H, (13)C, (29)Si) and ESI-MS.

  12. F4TCNQ on Cu, Ag, and Au as prototypical example for a strong organic acceptor on coinage metals

    NASA Astrophysics Data System (ADS)

    Rangger, Gerold M.; Hofmann, Oliver T.; Romaner, Lorenz; Heimel, Georg; Bröker, Benjamin; Blum, Ralf-Peter; Johnson, Robert L.; Koch, Norbert; Zojer, Egbert

    2009-04-01

    Metal work-function modification with the help of organic acceptors is an efficient tool to significantly enhance the performance of modern state-of-the-art organic molecular electronic devices. Here, the prototypical organic acceptor 2,3,5,6-tetrafluoro-7,7,8,8-tetracyanoquinodimethane, F4TCNQ, is characterized on Ag(111), Au(111), and Cu(111) metal surfaces by means of density-functional theory calculations. Particular attention is paid to charge-transfer processes at the metal-organic interface; a subtle balance between charge forward and backward donations in combination with a strong adsorption-induced geometry change are found to be responsible for the observed increase in the system work function. A larger effect is obtained for the metals with larger initial work function. Interestingly, this results in similar charge-injection barriers from the substrate metal into an organic semiconductor deposited on top of the F4TCNQ layer. The impact of the F4TCNQ packing density of the electronic properties of the interface is also addressed. Comparing the calculated energy-level alignments and work-function modifications to experimental data from ultraviolet photoelectron spectroscopy yields good agreement between experiments and simulations.

  13. 78 FR 31633 - Meeting of Citizen Coinage Advisory Committee

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-05-24

    ..., Conference Room A. Subject: Review and consideration of themes for the proposed Congressional Gold Medal for... design proposals relating to circulating coinage, bullion coinage, Congressional Gold Medals,...

  14. Shedding Light on the Photochemistry of Coinage-Metal Phosphorescent Materials: A Time-Resolved Laue Diffraction Study of an AgI-CuI Tetranuclear Complex

    SciTech Connect

    Jarzembska, Katarzyna N.; Kami,; #324; ski, Radoslaw; Fournier, Bertrand; Trzop, El; #380; bieta,; Sokolow, Jesse D.; Henning, Robert; Chen, Yang; Coppens, Philip

    2014-11-14

    The triplet excited state of a new crystalline form of a tetranuclear coordination d10–d10-type complex, Ag2Cu2L4 (L = 2-diphenylphosphino-3-methylindole ligand), containing AgI and CuI metal centers has been explored using the Laue pump–probe technique with ≈80 ps time resolution. The relatively short lifetime of 1 μs is accompanied by significant photoinduced structural changes, as large as the Ag1···Cu2 distance shortening by 0.59(3) Å. The results show a pronounced strengthening of the argentophilic interactions and formation of new Ag···Cu bonds on excitation. Theoretical calculations indicate that the structural changes are due to a ligand-to-metal charge transfer (LMCT) strengthening the Ag···Ag interaction, mainly occurring from the methylindole ligands to the silver metal centers. QM/MM optimizations of the ground and excited states of the complex support the experimental results. Comparison with isolated molecule optimizations demonstrates the restricting effect of the crystalline matrix on photoinduced distortions. The work represents the first time-resolved Laue diffraction study of a heteronuclear coordination complex and provides new information on the nature of photoresponse of coinage metal complexes, which have been the subject of extensive studies.

  15. 78 FR 59426 - Citizens Coinage Advisory Committee; Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-26

    ... United States Mint Citizens Coinage Advisory Committee; Meeting ACTION: Notification of Citizens Coinage..., section 5135(b)(8)(C), the United States Mint announces the Citizens Coinage Advisory Committee (CCAC.... Location: Conference Room A, United States Mint, 801 9th Street NW., Washington, DC 20220. Subject:...

  16. 76 FR 57806 - Citizens Coinage Advisory Committee Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-09-16

    ... United States Mint Citizens Coinage Advisory Committee Meeting ACTION: Notification of Citizens Coinage..., section 5135(b)(8)(C), the United States Mint announces the Citizens Coinage Advisory Committee (CCAC.... Location: Conference Room A, United States Mint, 801 9th Street, NW., Washington, DC 20220. Subject:...

  17. 76 FR 2754 - Citizens Coinage Advisory Committee Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-14

    ... United States Mint Citizens Coinage Advisory Committee Meeting ACTION: Notification of Citizens Coinage..., section 5135(b)(8)(C), the United States Mint announces the Citizens Coinage Advisory Committee (CCAC...: 8th Floor Board Room, United States Mint, 801 9th Street, NW., Washington, DC 20220. Subject:...

  18. 78 FR 57221 - Citizens Coinage Advisory Committee Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-17

    ... United States Mint Citizens Coinage Advisory Committee Meeting ACTION: Notification of Citizens Coinage..., section 5135(b)(8)(C), the United States Mint announces the Citizens Coinage Advisory Committee (CCAC... meeting at the United States Mint; 801 9th Street NW.; Washington, DC; Conference Room A. Subject:...

  19. 75 FR 70363 - Citizens Coinage Advisory Committee; Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-11-17

    ... United States Mint Citizens Coinage Advisory Committee; Meeting ACTION: Notification of Citizens Coinage..., section 5135(b)(8)(C), the United States Mint announces the Citizens Coinage Advisory Committee (CCAC...: 8th Floor Board Room, United States Mint, 801 9th Street, NW., Washington, DC 20220. Subject:...

  20. Interaction of Cu(+) with cytosine and formation of i-motif-like C-M(+)-C complexes: alkali versus coinage metals.

    PubMed

    Gao, Juehan; Berden, Giel; Rodgers, M T; Oomens, Jos

    2016-03-14

    The Watson-Crick structure of DNA is among the most well-known molecular structures of our time. However, alternative base-pairing motifs are also known to occur, often depending on base sequence, pH, or the presence of cations. Pairing of cytosine (C) bases induced by the sharing of a single proton (C-H(+)-C) may give rise to the so-called i-motif, which occurs primarily in expanded trinucleotide repeats and the telomeric region of DNA, particularly at low pH. At physiological pH, silver cations were recently found to stabilize C dimers in a C-Ag(+)-C structure analogous to the hemiprotonated C-dimer. Here we use infrared ion spectroscopy in combination with density functional theory calculations at the B3LYP/6-311G+(2df,2p) level to show that copper in the 1+ oxidation state induces an analogous formation of C-Cu(+)-C structures. In contrast to protons and these transition metal ions, alkali metal ions induce a different dimer structure, where each ligand coordinates the alkali metal ion in a bidentate fashion in which the N3 and O2 atoms of both cytosine ligands coordinate to the metal ion, sacrificing hydrogen-bonding interactions between the ligands for improved chelation of the metal cation.

  1. Structure and Energetics of Benzene Adsorbed on Transition-Metal Surfaces: Density-Functional Theory with Screened van der Waals Interactions

    NASA Astrophysics Data System (ADS)

    Liu, Wei; Ruiz-López, Victor G.; Zhang, Guo-Xu; Ren, Xinguo; Scheffler, Matthias; Tkatchenko, Alexandre

    2012-02-01

    The adsorption of benzene on metal surfaces is an important benchmark system for more complex hybrid inorganic/organic interfaces. Here, the recently developed DFT+vdW\\surfcirc method (density-functional theory including screened van der Waals (vdW) interactions) [1] is used to study the structure and energetics of benzene on transition-metal surfaces (Cu, Ag, Au, Pd, Pt, Rh, and Ir). Benzene adsorbs in a planar configuration at coinage metal surfaces, with almost zero distortion and a flat potential-energy surface. In contrast, benzene is strongly bound to the (111) surface of Pd, Pt, Rh, and Ir, and located at the bridge-30^o site. The vdW interactions significantly enhance the binding energy by more than 0.75 eV for all metals. The screening of the vdW energy plays a critical role in coinage metals, shortening the equilibrium distance by 0.2 å, and lowering the binding energy by 0.25 eV. The validity of our results is confirmed by comparison with calculations using the random-phase approximation including renormalized single excitations (EX+cRPA+rSE scheme [2]), and the experimental data from temperature-programmed desorption and calorimetry measurements. [1] V. G. Ruiz-L'opez et al., submitted. [2] X. Ren et al., Phys. Rev. Lett. 106, 153003 (2011).

  2. The Role of Weak Interactions in Strong Intermolecular M···Cl Complexes of Coinage Metal Pyrazolates: Spectroscopic and DFT Study.

    PubMed

    Titov, Aleksei A; Guseva, Ekaterina A; Filippov, Oleg A; Babakhina, Galina M; Godovikov, Ivan A; Belkova, Natalia V; Epstein, Lina M; Shubina, Elena S

    2016-09-08

    The nondestructive reversible complexation of the macrocyclic group 11 metal pyrazolates {[3,5-(CF3)2Pz]M}3 (M = Cu(I), Ag(I)) to the halogen atom X = Cl, Br of η(3)-allyliron tricarbonyl halides (η(3)-2-R-C3H4)Fe(CO)3X is revealed by the variable-temperature spectroscopic (IR, NMR) study combined with density functional theory calculations. The composition of all complexes at room temperature is determined as 1:1. In the case of the [AgL]3 macrocycle, complexes 1:2 are observed at low temperature (<260 K). The complex's stability depends on the substituents in the allyl fragment and halide ligand as well as on the metal atom (Ag(I), Cu(I)) in the macrocycle. For bulky substituents (Me and Ph) the endo/exo equilibrium of the parent (η(3)-2-R-C3H4)Fe(CO)3X shifts upon the complex formation in favor of the exo isomer due to additional noncovalent interactions of the substituent with macrocycle.

  3. 78 FR 14154 - Citizens Coinage Advisory Committee; Public Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-03-04

    ... United States Mint Citizens Coinage Advisory Committee; Public Meeting ACTION: Notification of Citizens... 31, section 5135(b)(8)(C), the United States Mint announces the Citizens Coinage Advisory Committee.... Location: Conference Room A, United States Mint, 801 9th Street NW., Washington, DC 20220. Subject:...

  4. 78 FR 36034 - Citizens Coinage Advisory Committee; Public Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-06-14

    ... United States Mint Citizens Coinage Advisory Committee; Public Meeting ACTION: Notification of Citizens... 31, section 5135(b)(8)(C), the United States Mint announces the Citizens Coinage Advisory Committee.... Location: Conference Room A, United States Mint, 801 9th Street NW., Washington, DC 20220. Subject:...

  5. 78 FR 23635 - Citizens Coinage Advisory Committee; Public Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-04-19

    ... United States Mint Citizens Coinage Advisory Committee; Public Meeting ACTION: Notification of Citizens... 31, section 5135(b)(8)(C), the United States Mint announces the Citizens Coinage Advisory Committee.... Location: Conference Room A, United States Mint, 801 9th Street NW., Washington, DC 20220. Subject:...

  6. Antibacterial Metallic Touch Surfaces

    PubMed Central

    Villapún, Victor M.; Dover, Lynn G.; Cross, Andrew; González, Sergio

    2016-01-01

    Our aim is to present a comprehensive review of the development of modern antibacterial metallic materials as touch surfaces in healthcare settings. Initially we compare Japanese, European and US standards for the assessment of antimicrobial activity. The variations in methodologies defined in these standards are highlighted. Our review will also cover the most relevant factors that define the antimicrobial performance of metals, namely, the effect of humidity, material geometry, chemistry, physical properties and oxidation of the material. The state of the art in contact-killing materials will be described. Finally, the effect of cleaning products, including disinfectants, on the antimicrobial performance, either by direct contact or by altering the touch surface chemistry on which the microbes attach, will be discussed. We offer our outlook, identifying research areas that require further development and an overview of potential future directions of this exciting field. PMID:28773856

  7. Spectroscopic characterization of the on-surface induced (cyclo)dehydrogenation of a N-heteroaromatic compound on noble metal surfaces.

    PubMed

    Palacio, I; Pinardi, A L; Martínez, J I; Preobrajenski, A; Cossaro, A; Jancarik, A; Stará, I; Starý, I; Méndez, J; Martín-Gago, J A; López, M F

    2017-08-23

    New nanoarchitectures can be built from polycyclic aromatic hydrocarbons (PAHs) by exploiting the capability of some metal surfaces for inducing cyclodehydrogenation reactions. This bottom-up approach allows the formation of nanostructures with a different dimensionality from the same precursor as a consequence of the diffusion and coupling of the PAHs adsorbed on the surface. In this work we present a thorough study, by means of a combination of X-ray photoemission spectroscopy, near-edge X-ray absorption fine structure and scanning tunneling microscopy with first principle calculations of the structural and chemical transformations undergone by pyridyl-substituted dibenzo[5]helicene on three coinage surfaces, namely Cu(110), Cu(111) and Au(111). Upon annealing, on-surface chemical reactions are promoted affecting the adsorbate/substrate and the molecule/molecule interactions. This thermally induced process favours the transformation from diffusing isolated molecules to polymeric nanographene chains and finally to N-doped graphene.

  8. SURFACE TREATMENT OF METALLIC URANIUM

    DOEpatents

    Gray, A.G.; Schweikher, E.W.

    1958-05-27

    The treatment of metallic uranium to provide a surface to which adherent electroplates can be applied is described. Metallic uranium is subjected to an etchant treatment in aqueous concentrated hydrochloric acid, and the etched metal is then treated to dissolve the resulting black oxide and/or chloride film without destroying the etched metal surface. The oxide or chloride removal is effected by means of moderately concentrated nitric acid in 3 to 20 seconds.

  9. Metal radii in surface science

    NASA Astrophysics Data System (ADS)

    Campbell, Charles T.

    1986-03-01

    The saturation monolayer coverage of an adsorbed metal overlayer on a smooth metal surface is largely determined by the adsorbed metal's radius. Experimental maximum packing densities in two-dimensional metal overlayers are compared with predictions based on several different definitions of metal atom radii: atomic radii, covalent radii, minimum bulk interatomic distance (:2) and the Zachariasen [J. Inorg. Nucl. Chem. 35 (1973) 3487] metal radii. Best agreement is found with the last, which is obtained by assuming that the bulk, pure metal density is obtained from an ideal, hexagonal close-packed structure of spheres of that radius.

  10. Metal radii in surface science

    NASA Astrophysics Data System (ADS)

    Campbell, Charles T.

    The saturation monolayer coverage of an adsorbed metal overlayer on a smooth metal surface is largely determined by the adsorbed metal's radius. Experimental maximum packing densities in two-dimensional metal overlayers are compared with predictions based on several different definitions of metal atom radii: atomic radii, covalent radii, minimum bulk interatomic distance (: 2) and the Zachariasen [J. Inorg. Nucl. Chem. 35 (1973) 3487] metal radii. Best agreement is found with the last, which is obtained by assuming that the bulk, pure metal density is obtained from an ideal, hexagonal close-packed structure of spheres of that radius.

  11. Corrosion-resistant metal surfaces

    DOEpatents

    Sugama, Toshifumi

    2009-03-24

    The present invention relates to metal surfaces having thereon an ultrathin (e.g., less than ten nanometer thickness) corrosion-resistant film, thereby rendering the metal surfaces corrosion-resistant. The corrosion-resistant film includes an at least partially crosslinked amido-functionalized silanol component in combination with rare-earth metal oxide nanoparticles. The invention also relates to methods for producing such corrosion-resistant films.

  12. 75 FR 34215 - Notification of Citizens Coinage Advisory Committee June 28, 2010 Public Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-06-16

    ... design quality. Interested persons should call 202-354-7502 for the latest update on meeting time and... any theme or design proposals relating to circulating coinage, bullion coinage, Congressional...

  13. METAL SURFACE TREATMENT

    DOEpatents

    Eubank, L.D.

    1958-08-12

    Improved flux baths are described for use in conjunction with hot dipped coatings for uranium. The flux bath consists of molten alkali metal, or alkaline earth metal halides. One preferred embodiment comprises a bath containing molten KCl, NaCl, and LiCl in proportions approximating the triple eutectic.

  14. Metallic surfaces with special wettability

    NASA Astrophysics Data System (ADS)

    Liu, Kesong; Jiang, Lei

    2011-03-01

    Metals are important and irreplaceable engineered materials in our society. Nature is a school for scientists and engineers, which has long served as a source of inspiration for humans. Inspired by nature, a variety of metallic surfaces with special wettability have been fabricated in recent years through the combination of surface micro- and nanostructures and chemical composition. These metallic surfaces with special wettability exhibit important applications in anti-corrosion, microfluidic systems, oil-water separation, liquid transportation, and other fields. Recent achievements in the fabrication and application of metallic surfaces with special wettability are presented in this review. The research prospects and directions of this field are also briefly addressed. We hope this review will be beneficial to expand the practical applications of metals and offer some inspirations to the researchers in the fields of engineering, biomedicine, and materials science.

  15. Surface stress of stepped chiral metal surfaces.

    PubMed

    Blanco-Rey, M; Pratt, S J; Jenkins, S J

    2009-01-16

    The use of surface stress as a physical probe for examining chiral effects in surfaces is proposed. First-principles calculations of the surface stress in stepped achiral and chiral bcc metal surfaces (Fe, Mo, and W) are presented. When no mirror symmetry is present, principal stress orientations are unconstrained; nevertheless, we find that the stress is smoothly varying along a suitably chosen stereographic zone of surfaces. Stress ellipses for Fe differ qualitatively from those of Mo and W, suggesting that its surface stress has a distinct origin.

  16. Electrochemistry of Metal Surfaces

    DTIC Science & Technology

    1990-06-30

    1-butene (BTE), 1-pentene (PTE), l-hexene (HXE), 1-- octene (OCE) and l--decene (DCE). Vibrational spectra of the adsorbed layers were obtained by use...Surface Sci., 92, 617 (1980). 39. Electrochemical Hydrogenation of Ethylene at Well-Defined Pt(100) and Pt(111) Surfaces. Arthur T. Hubbard, Mark A...Surf Sci., 147, 241 (1984). 75. A Comparison of Gas Phase and Electrochemical Hydrogenation of Ethylene at ** Platinum Surfaces. Andrzej Wieckowski

  17. Formation of single-walled bimetallic coinage alloy nanotubes in confined carbon nanotubes: molecular dynamics simulations.

    PubMed

    Han, Yang; Zhou, Jian; Dong, Jinming; Yoshiyuki, Kawazoe

    2013-10-28

    The growth of single-walled bimetallic Au-Ag, Au-Cu and Ag-Cu alloy nanotubes (NTs) and nanowires (NWs) in confined carbon nanotubes (CNTs) has been investigated by using the classical molecular dynamics (MD) method. It is found that three kinds of single-walled gold-silver, gold-copper and silver-copper alloy NTs could indeed be formed in confined CNTs at any alloy concentration, whose geometric structures are less sensitive to the alloy concentration. And an extra nearly pure Au (Cu) chain will exist at the center of Au-Ag (Au-Cu and Ag-Cu) NTs when the diameters of the outside CNTs are big enough, thus producing a new type of tube-like alloy NWs. The bonding energy differences between the mono- and hetero-elements of the coinage metal atoms and the quasi-one-dimensional confinement from the CNT play important roles in suppressing effectively the "self-purification" effects, leading to formation of these coinage alloy NTs. In addition, the fluid-solid phase transition temperatures of the bimetallic alloy NTs are found to locate between those of the corresponding pure metal tubes. Finally, the dependences of the radial breathing mode (RBM) frequencies and the tube diameters of the alloy NTs on the alloying concentration were obtained, which will be very helpful for identifying both the alloying concentration and the alloy tube diameters in future experiments.

  18. Decontaminating metal surfaces

    DOEpatents

    Childs, Everett L.

    1984-11-06

    Radioactively contaminated surfaces can be electrolytically decontaminated with greatly increased efficiencies by using electrolytes containing higher than heretofore conventional amounts of nitrate, e.g.,>600 g/l of NaNO.sub.3, or by using nitrate-containing electrolytes which are acidic, e.g., of a pH<6.

  19. Decontaminating metal surfaces

    DOEpatents

    Childs, E.L.

    1984-01-23

    Radioactively contaminated surfaces can be electrolytically decontaminated with greatly increased efficiencies by using electrolytes containing higher than heretofore conventional amounts of nitrate, e.g., >600 g/1 of NaNO/sub 3/, or by using nitrate-containing electrolytes which are acidic, e.g., of a pH < 6.

  20. Surface Electrochemistry of Metals

    DTIC Science & Technology

    1993-04-30

    171.** Auger Electron Angular Distributions from Underpotentially Deposited Ag Monolayers and Films at Pt(I 11) Pretreated with Iodine. Charles A...chemical vapor deposition (RTCVD), in which the heated Si(100) surface was carbonized with propane. Auger emission angular distributions were measured

  1. Lotus-like effect for metal filings recovery and particle removal on heated metal surfaces using Leidenfrost water droplets.

    PubMed

    Tan, Cher Lin Clara; Sapiha, Kostantyn; Leong, Yoke Fun Hannah; Choi, Siwon; Anariba, Franklin; Thio, Beng Joo Reginald

    2015-07-21

    A "lotus-like" effect is applied to demonstrate the ability of the Leidenfrost water droplets to recover Cu particles on a heated Al substrate. Cu particles on the heated surface adhere to the rim of the Leidenfrost droplets and eventually coat the droplets' surface to form an aggregation. When Fe filings are added to the Cu particles, the aggregated mixture can then be collected using a strong rare earth magnet (NdFeB) upon evaporation of the water. We also show that the Leidenfrost effect can be effectively utilized to recover both hydrophobic (dust and activated carbon) and hydrophilic (SiO2 and MgO) particles from heated Al surfaces without any topographical modification or surfactant addition. Our results show that hydrophobic and hydrophilic materials can be collected with >92% and >96% effectiveness on grooved and smooth Al surfaces, respectively. Furthermore, we observed no significant differences in the amount of material collected above the Leidenfrost point within the tested temperature range (240 °C vs. 340 °C) as well as when the Al sheet was replaced with a Cu sheet as the substrate. However, we did observe that the Leidenfrost droplets were able to collect a greater amount of material when the working liquid was water than when it was ethanol. Our findings show promise in the development of an effective precious coinage metal filings recovery technology for application in the mint industry, as well as the self-cleaning of metallic and semiconductor surfaces where manual cleaning is not amenable.

  2. Modeling Adsorption and Reactions of Organic Molecules at Metal Surfaces

    PubMed Central

    2014-01-01

    response effects enables reliable modeling of structure and stability for a broad class of organic molecules adsorbed on metal surfaces. This method was demonstrated to achieve quantitative accuracy for aromatic hydrocarbons (benzene, naphthalene, anthracene, and diindenoperylene), C60, and sulfur/oxygen-containing molecules (thiophene, NTCDA, and PTCDA) on close-packed and stepped metal surfaces, leading to an overall accuracy of 0.1 Å in adsorption heights and 0.1 eV in binding energies with respect to state-of-the-art experiments. An unexpected finding is that vdW interactions contribute more to the binding of strongly bound molecules on transition-metal surfaces than for molecules physisorbed on coinage metals. The accurate inclusion of vdW interactions also significantly improves tilting angles and adsorption heights for all the studied molecules, and can qualitatively change the potential-energy surface for adsorbed molecules with flexible functional groups. Activation barriers for molecular switches and reaction precursors are modified as well. PMID:24915492

  3. Modeling adsorption and reactions of organic molecules at metal surfaces.

    PubMed

    Liu, Wei; Tkatchenko, Alexandre; Scheffler, Matthias

    2014-11-18

    response effects enables reliable modeling of structure and stability for a broad class of organic molecules adsorbed on metal surfaces. This method was demonstrated to achieve quantitative accuracy for aromatic hydrocarbons (benzene, naphthalene, anthracene, and diindenoperylene), C60, and sulfur/oxygen-containing molecules (thiophene, NTCDA, and PTCDA) on close-packed and stepped metal surfaces, leading to an overall accuracy of 0.1 Å in adsorption heights and 0.1 eV in binding energies with respect to state-of-the-art experiments. An unexpected finding is that vdW interactions contribute more to the binding of strongly bound molecules on transition-metal surfaces than for molecules physisorbed on coinage metals. The accurate inclusion of vdW interactions also significantly improves tilting angles and adsorption heights for all the studied molecules, and can qualitatively change the potential-energy surface for adsorbed molecules with flexible functional groups. Activation barriers for molecular switches and reaction precursors are modified as well.

  4. 77 FR 67736 - Citizens Coinage Advisory Committee; Public Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-11-13

    ... Program Coins honoring Great Smoky Mountains National Park, Shenandoah National Park, Arches National Park, Great Sand Dunes National Park, and Everglades National Park; review and consideration of candidate... Secretary of the Treasury on any theme or design proposals relating to circulating coinage, bullion...

  5. 76 FR 34811 - Citizens Coinage Advisory Committee Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-06-14

    ... calendar years; and discussion on coin design quality. Interested persons should call 202-354-7502 for the... and discussion of the candidate designs for the reverse of the 2012 Native American $1 Coin... Secretary of the Treasury on any theme or design proposals relating to circulating coinage, bullion...

  6. Magnetoelectric coupling at metal surfaces.

    PubMed

    Gerhard, L; Yamada, T K; Balashov, T; Takács, A F; Wesselink, R J H; Däne, M; Fechner, M; Ostanin, S; Ernst, A; Mertig, I; Wulfhekel, W

    2010-11-01

    Magnetoelectric coupling allows the magnetic state of a material to be changed by an applied electric field. To date, this phenomenon has mainly been observed in insulating materials such as complex multiferroic oxides. Bulk metallic systems do not exhibit magnetoelectric coupling, because applied electric fields are screened by conduction electrons. We demonstrate strong magnetoelectric coupling at the surface of thin iron films using the electric field from a scanning tunnelling microscope, and are able to write, store and read information to areas with sides of a few nanometres. Our work demonstrates that high-density, non-volatile information storage is possible in metals.

  7. METHOD OF CLEANING METAL SURFACES

    DOEpatents

    Winkler, H.W.; Morfitt, J.W.; Little, T.H.

    1959-05-19

    Cleaning fluids for removing deposits from metal surfaces are described. The cleaning agents of the invention consist of aqueous nitric acid and an amhydrous nitrate salt of a metal which is lower in the electromotive series than the element of the deposit to be removed. In general, the salt content of thc cleaning agents ranged from 10 to 90%, preferably from 10 to 40% by weight; and the balance of the composition comprises nitric acid of any strength from extremely dilute up to concentrated strength.

  8. Laser cleaning of metal surfaces

    NASA Astrophysics Data System (ADS)

    Walters, Craig T.; Campbell, Bernard E.; Hull, Robert J.

    1998-09-01

    There is a critical need to replace ozone-depleting substances and hazardous chemicals that, in the past, have been used routinely in aerospace maintenance operations such as precision cleaning of metal surfaces. Lasers now offer the potential for removal of many organic materials from metals without the use of any solvent or aqueous cleaning agents. This paper presents quantitative results of laser-cleaning process-development research with a pulsed Nd:YAG laser and several common metals and organic contaminants. Metal coupons of Stainless Steel 304, Aluminum 5052, and Titanium were contaminated with known amounts of organic oils and greases at contamination levels in the 5 to 200 (mu) g/cm2 range. A fiber-optic-delivered 1064-nm pulsed laser beam (20-Hz repetition rate) was scanned over the coupons with different overlap and pulse fluence conditions. Measurements of mass loss revealed that all levels of initial contamination could be removed to final cleanliness levels less than 3 (mu) g/cm2, at which point the mass loss measurements became uncertain. Pulse fluence thresholds for initial cleaning effects and practical cleaning rates for several metal and contaminant combinations are reported. From the totality of the results, an overall picture of the contaminant removal mechanism is emerging. For semi-transparent films, it is conjectured that a thermo-mechanical effect occurs wherein the laser energy is absorbed predominantly in the metal substrate which expands on the nanosecond time scale. This rapid expansion, in combination with some material evaporation at the film/metal interface, is believed to eject the contaminant film directly into aerosol droplets/particles which can be swept away and collected for recycle or cost- effective disposal in a compact form. Evidence for this mechanism will be presented.

  9. Laser Interaction with Metallic Surfaces.

    DTIC Science & Technology

    1982-12-01

    opaque targets the absorptance is one m~nus the reflectance , measurement of the time dependence of the metal surface reflectance will yield the laser...1O 4 TIME (ps) TIME (ns) (a) REFLECTANCE MEASUREMENTS (b) GENERAL REFLECTANCE WC) REFLECTANCE MEASUREMENT OF SONCH-8RUEVICH et al CURVE OF ZAVECZ et al...integrating sphere by Bonch-Bruevich and, therefore, a total reflectance measurement while Zavecz et al. measured only the specular reflectance. In

  10. Method for decontamination of radioactive metal surfaces

    DOEpatents

    Bray, L.A.

    1996-08-13

    Disclosed is a method for removing radioactive contaminants from metal surfaces by applying steam containing an inorganic acid and cerium IV. Cerium IV is applied to contaminated metal surfaces by introducing cerium IV in solution into a steam spray directed at contaminated metal surfaces. Cerium IV solution is converted to an essentially atomized or vapor phase by the steam.

  11. Method for decontamination of radioactive metal surfaces

    DOEpatents

    Bray, Lane A.

    1996-01-01

    Disclosed is a method for removing radioactive contaminants from metal surfaces by applying steam containing an inorganic acid and cerium IV. Cerium IV is applied to contaminated metal surfaces by introducing cerium IV in solution into a steam spray directed at contaminated metal surfaces. Cerium IV solution is converted to an essentially atomized or vapor phase by the steam.

  12. Structured surfaces on metal optics

    NASA Astrophysics Data System (ADS)

    Steinkopf, Ralf; Hartung, Johannes; Kinast, Jan; Gebhardt, Andreas; Risse, Stefan; Eberhardt, Ramona

    2015-09-01

    Diamond machining of metal optics is a flexible way to manufacture structured elements on different surface geometries. Especially curved substrates such as spheres, aspheres, or freeforms in combination with structured elements enable innovative products like headlights of automobiles or spectrometers in life science or space applications. Using diamond turning, servo turning, milling, and shaping, different technologies for arbitrary geometries are available. The addressed wavelengths are typically in the near- infrared (NIR) and infrared (IR) spectral range. Applying additional finishing processes, diamond machining is also used for optics applicable down to the EUV spectral range. This wide range of applications is represented in the used materials, too. However, one important material group for diamond machining is metal substrates. For diamond machining of structured surfaces, it is important to consider the microstructure of the utilized materials thoroughly. Especially amorphous materials as nickel-phosphorus alloys or fine-grained copper allow the fine structuring of refractive and diffractive structures. The paper analyzes the influence variables for diamond machining of structured surfaces and shows the use of this research for applications in the spectral range from IR to EUV.

  13. 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.

  14. Surface chemistry of liquid metals

    NASA Technical Reports Server (NTRS)

    Mann, J. Adin, Jr.; Peebles, Henry; Peebles, Diamond; Rye, Robert; Yost, Fred

    1993-01-01

    The fundamental surface chemistry of the behavior of liquid metals spreading on a solid substrate is not at all well understood. Each of these questions involves knowing the details of the structure of interfaces and their dynamics. For example the structure of a monolayer of tin oxide on pure liquid tin is unknown. This is in contrast to the relatively large amount of data available on the structure of copper oxide monolayers on solid, pure copper. However, since liquid tin has a vapor pressure below 10(exp -10)torr for a reasonable temperature range above its melting point, it is possible to use the techniques of surface science to study the geometric, electronic and vibrational structures of these monolayers. In addition, certain techniques developed by surface chemists for the study of liquid systems can be applied to the ultra-high vacuum environment. In particular we have shown that light scattering spectroscopy can be used to study the surface tension tensor of these interfaces. The tin oxide layer in particular is very interesting in that the monolayer is rigid but admits of bending. Ellipsometric microscopy allows the visualization of monolayer thick films and show whether island formation occurs at various levels of dosing.

  15. Coinage metals binding as main group elements: structure and bonding of the carbene complexes [TM(cAAC)2] and [TM(cAAC)2](+) (TM = Cu, Ag, Au).

    PubMed

    Jerabek, Paul; Roesky, Herbert W; Bertrand, Guy; Frenking, Gernot

    2014-12-10

    Quantum chemical calculations using density functional theory have been carried out for the cyclic (alkyl)(amino)carbene (cAAC) complexes of the group 11 atoms [TM(cAAC)2] (TM = Cu, Ag, Au) and their cations [TM(cAAC)2](+). The nature of the metal-ligand bonding was investigated with the charge and energy decomposition analysis EDA-NOCV. The calculations show that the TM-C bonds in the charged adducts [TM(cAAC)2](+) are significantly longer than in the neutral complexes [TM(cAAC)2], but the cations have much higher bond dissociation energies than the neutral molecules. The intrinsic interaction energies ΔEint in [TM(cAAC)2](+) take place between TM(+) in the (1)S electronic ground state and (cAAC)2. In contrast, the metal-ligand interactions in [TM(cAAC)2] involve the TM atoms in the excited (1)P state yielding strong TM p(π) → (cAAC)2 π backdonation, which is absent in the cations. The calculations suggest that the cAAC ligands in [TM(cAAC)2] are stronger π acceptors than σ donors. The trends of the intrinsic interaction energies and the bond dissociation energies of the metal-ligand bonds in [TM(cAAC)2] and [TM(cAAC)2](+) give the order Au > Cu > Ag. Calculations at the nonrelativistic level give weaker TM-C bonds, particularly for the gold complexes. The trend for the bond strength in the neutral and charged adducts without relativistic effects becomes Cu > Ag > Au. The EDA-NOCV calculations suggest that the weaker bonds at the nonrelativistic level are mainly due to stronger Pauli repulsion and weaker orbital interactions. The NBO picture of the C-TM-C bonding situation does not correctly represent the nature of the metal-ligand interactions in [TM(cAAC)2].

  16. Refractory thermal insulation for smooth metal surfaces

    NASA Technical Reports Server (NTRS)

    1964-01-01

    To protect rocket metal surfaces from engine exhaust heat, a refractory thermal insulation mixture, which adheres to smooth metals, has been developed. Insulation protection over a wide temperature range can be controlled by thickness of the applied mixture.

  17. Synthesis metal nanoparticle

    DOEpatents

    Bunge, Scott D.; Boyle, Timothy J.

    2005-08-16

    A method for providing an anhydrous route for the synthesis of amine capped coinage-metal (copper, silver, and gold) nanoparticles (NPs) using the coinage-metal mesityl (mesityl=C.sub.6 H.sub.2 (CH.sub.3).sub.3 -2,4,6) derivatives. In this method, a solution of (Cu(C.sub.6 H.sub.2 (CH.sub.3).sub.3).sub.5, (Ag(C.sub.6 H.sub.2 (CH.sub.3).sub.3).sub.4, or (Au(C.sub.6 H.sub.2 (CH.sub.3).sub.3).sub.5 is dissolved in a coordinating solvent, such as a primary, secondary, or tertiary amine; primary, secondary, or tertiary phosphine, or alkyl thiol, to produce a mesityl precursor solution. This solution is subsequently injected into an organic solvent that is heated to a temperature greater than approximately 100.degree. C. After washing with an organic solvent, such as an alcohol (including methanol, ethanol, propanol, and higher molecular-weight alcohols), oxide free coinage NP are prepared that could be extracted with a solvent, such as an aromatic solvent (including, for example, toluene, benzene, and pyridine) or an alkane (including, for example, pentane, hexane, and heptane). Characterization by UV-Vis spectroscopy and transmission electron microscopy showed that the NPs were approximately 9.2.+-.2.3 nm in size for Cu.degree., (no surface oxide present), approximately 8.5.+-.1.1 nm Ag.degree. spheres, and approximately 8-80 nm for Au.degree..

  18. Electrochemical nitridation of metal surfaces

    DOEpatents

    Wang, Heli; Turner, John A.

    2015-06-30

    Electrochemical nitridation of metals and the produced metals are disclosed. An exemplary method of electrochemical nitridation of metals comprises providing an electrochemical solution at low temperature. The method also comprises providing a three-electrode potentiostat system. The method also comprises stabilizing the three-electrode potentiostat system at open circuit potential. The method also comprises applying a cathodic potential to a metal.

  19. The interaction of a metal deactivator with metal surfaces

    SciTech Connect

    Schreifels, J.A. ); Morris, R.E.; Turner, N.H.; Mowery, R.L. )

    1990-01-01

    In modern aircraft fuel systems, the fuel is used as a heat transfer medium to dissipate heat from the avionics and hydraulic systems. Under these conditions, the fuel can undergo autooxidations. Autooxidations of net fuel can result in the formation of insoluble gum and sediment which can impair operation of the jet engine. Metal deactivator additives (MDA) were developed to counteract the catalytic activity of dissolved metals. The authors have directed their efforts at ascertaining the various mechanisms by which MDA can act, particularly in accelerated stability testing. One objective of this study was to determine to what extent interactions with metal surfaces of the test apparent govern the effectiveness of metal deactivators. This paper describes an examination of metal surfaces exposed to MDA solutions to determine under what, if any, conditions metal passivation can occur.

  20. Surface states, surface metal-insulator, and surface insulator-metal transitions

    NASA Astrophysics Data System (ADS)

    Tosatti, E.

    1995-05-01

    An informal discussion of various cases where two-dimensional surface metal-insulator structural and charge-density-wave instabilities driven by partly filled surface states have been advocated is presented. These include reconstructions of clean semiconductor surfaces and of W(100) and Mo(100), as well as anomalies on the hydrogen-covered surfaces H/W(110) and H/Mo(110), and possibly alkali-covered surfaces such as K/Cu(111). In addition, there is a discussion of the opposite type of phenomena, namely surface insulator-metal transitions, which can be argued to occur on (alpha)-Ga(001), high-temperature Ge(111), and probably Be(0001).

  1. Surface protected lithium-metal-oxide electrodes

    DOEpatents

    Thackeray, Michael M.; Kang, Sun-Ho

    2016-04-05

    A lithium-metal-oxide positive electrode having a layered or spinel structure for a non-aqueous lithium electrochemical cell and battery is disclosed comprising electrode particles that are protected at the surface from undesirable effects, such as electrolyte oxidation, oxygen loss or dissolution by one or more lithium-metal-polyanionic compounds, such as a lithium-metal-phosphate or a lithium-metal-silicate material that can act as a solid electrolyte at or above the operating potential of the lithium-metal-oxide electrode. The surface protection significantly enhances the surface stability, rate capability and cycling stability of the lithium-metal-oxide electrodes, particularly when charged to high potentials.

  2. Vacancy Transport and Interactions on Metal Surfaces

    DTIC Science & Technology

    2014-03-06

    AFRL-OSR-VA-TR-2013-0317 VACANCY TRANSPORT AND INTERACTIONS ON METAL SURFACES Gert Ehrlich UNIVERSITY OF ILLINOIS CHAMPAIGN Final Report 03/06/2014...30, 2012 Gert Ehrlich , PI Abstract This proposal is a study of vacancy transport and vacancy interaction on metal surfaces. Adatom self...Trembułowicz, Gert Ehrlich , Grażyna Antczak,Surface diffusion of gold on quasihexagonal-reconstructed Au(100) ,Physical Review B 84 (2011) 245445-1

  3. Frictional effects near a metal surface

    SciTech Connect

    Dou, Wenjie; Subotnik, Joseph E.; Nitzan, Abraham

    2015-08-07

    When a classical master equation (CME) is used to describe the nonadiabatic dynamics of a molecule at metal surfaces, we show that in the regime of reasonably strong molecule-metal couplings, the CME can be reduced to a Fokker-Planck equation with an explicit form of electronic friction. For a single metal substrate at thermal equilibrium, the electronic friction and random force satisfy the fluctuation-dissipation theorem. When we investigate the time scale for an electron transfer (ET) event between the molecule and metal surface, we find that the ET rates show a turnover effect (just as in Kramer’s theory) as a function of frictional damping.

  4. 75 FR 6791 - Notification of Citizens Coinage Advisory Committee February 2010 Public Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-02-10

    ... 9th Street NW., Washington, DC 20220. Subject: Review 2011 First Spouse Gold Coin and Medal Program..., bullion coinage, Congressional Gold Medals, and national and other medals. Advises the Secretary of...

  5. Metallic superhydrophobic surfaces via thermal sensitization

    NASA Astrophysics Data System (ADS)

    Vahabi, Hamed; Wang, Wei; Popat, Ketul C.; Kwon, Gibum; Holland, Troy B.; Kota, Arun K.

    2017-06-01

    Superhydrophobic surfaces (i.e., surfaces extremely repellent to water) allow water droplets to bead up and easily roll off from the surface. While a few methods have been developed to fabricate metallic superhydrophobic surfaces, these methods typically involve expensive equipment, environmental hazards, or multi-step processes. In this work, we developed a universal, scalable, solvent-free, one-step methodology based on thermal sensitization to create appropriate surface texture and fabricate metallic superhydrophobic surfaces. To demonstrate the feasibility of our methodology and elucidate the underlying mechanism, we fabricated superhydrophobic surfaces using ferritic (430) and austenitic (316) stainless steels (representative alloys) with roll off angles as low as 4° and 7°, respectively. We envision that our approach will enable the fabrication of superhydrophobic metal alloys for a wide range of civilian and military applications.

  6. Surface treatment using metal foil liner

    NASA Technical Reports Server (NTRS)

    Garvey, Ray

    1989-01-01

    A metal foil liner can be used to seal large area surfaces. Characteristics of the two-layer foil liner are discussed. Micrographs for foil-to-foil, foil-to-composite, visible seams, and hidden seams are examined.

  7. Surface plasmon lifetime in metal nanoshells

    NASA Astrophysics Data System (ADS)

    Kirakosyan, Arman S.; Stockman, Mark I.; Shahbazyan, Tigran V.

    2016-10-01

    The lifetime of localized surface plasmon plays an important role in many aspects of plasmonics and its applications. In small metal nanostructures, the dominant mechanism of plasmon decay is size-dependent Landau damping. We performed quantum-mechanical calculations of Landau damping for the bright surface plasmon mode in a metal nanoshell with dielectric core. In contrast to the conventional model based on the electron surface scattering, we found that the damping rate decreases as the nanoshell thickness is reduced. The origin of this behavior is traced to the spatial distribution of plasmon local field in the metal shell. We also found that, due to the interference of electron scattering amplitudes from the two nanoshell metal surfaces, the damping rate exhibits pronounced quantum beats with changing shell thickness.

  8. Electromagnetic force on structured metallic surfaces

    NASA Astrophysics Data System (ADS)

    Velzen, Andrew H.; Webb, Kevin J.

    2015-09-01

    We present a method by which the relatively weak electromagnetic force exerted on a surface can be dramatically enhanced. By structuring a metal surface at the nanoscale, we show that the force can be substantially increased over that on the planar metallic surface. The basis for this effect is found to be cavity-enhanced fields and the excitation of surface waves, and results are related to theory. In practice, this force enhancement could be expanded to other materials in various frequency regimes. This increased electromagnetic force should facilitate an expansion of applications related to optomechanics.

  9. Nonadiabatic dynamics at metal surfaces: Independent-electron surface hopping

    NASA Astrophysics Data System (ADS)

    Shenvi, Neil; Roy, Sharani; Tully, John C.

    2009-05-01

    Recent experiments have shown convincing evidence for nonadiabatic energy transfer from adsorbate degrees of freedom to surface electrons during the interaction of molecules with metal surfaces. In this paper, we propose an independent-electron surface hopping algorithm for the simulation of nonadiabatic gas-surface dynamics. The transfer of energy to electron-hole pair excitations of the metal is successfully captured by hops between electronic adiabats. The algorithm is able to account for the creation of multiple electron-hole pairs in the metal due to nonadiabatic transitions. Detailed simulations of the vibrational relaxation of nitric oxide on a gold surface, employing a multistate potential energy surface fit to density functional theory calculations, confirm that our algorithm can capture the underlying physics of the inelastic scattering process.

  10. Sulfur-induced structural motifs on copper and gold surfaces

    SciTech Connect

    Walen, Holly

    2016-01-01

    The interaction of sulfur with copper and gold surfaces plays a fundamental role in important phenomena that include coarsening of surface nanostructures, and self-assembly of alkanethiols. Here, we identify and analyze unique sulfur-induced structural motifs observed on the low-index surfaces of these two metals. We seek out these structures in an effort to better understand the fundamental interactions between these metals and sulfur that lends to the stability and favorability of metal-sulfur complexes vs. chemisorbed atomic sulfur. The experimental observations presented here—made under identical conditions—together with extensive DFT analyses, allow comparisons and insights into factors that favor the existence of metal-sulfur complexes, vs. chemisorbed atomic sulfur, on metal terraces. We believe this data will be instrumental in better understanding the complex phenomena occurring between the surfaces of coinage metals and sulfur.

  11. Method of boronizing transition metal surfaces

    DOEpatents

    Koyama, Koichiro; Shimotake, Hiroshi.

    1983-08-16

    A method is presented for preparing a boride layer on a transition metal substrate for use in corrosive environments or as a harden surface in machine applications. This method is particularly useful in treating current collectors for use within a high temperature and corrosive electrochemical cell environment. A melt of a alkali metal boride tetrafluoride salt including such as KF to lower its melting point is prepared including a dissolved boron containing material, for instance NiB, MnB[sub 2], or CrB[sub 2]. A transition metal to be coated is immersed in the melt at a temperature of no more than 700 C and a surface boride layer of that transition metal is formed within a period of about 24 hours on the substrate surface. 4 figs.

  12. Method of boronizing transition metal surfaces

    DOEpatents

    Koyama, Koichiro; Shimotake, Hiroshi

    1983-01-01

    A method is presented for preparing a boride layer on a transition metal substrate for use in corrosive environments or as a harden surface in machine applications. This method is particularly useful in treating current collectors for use within a high temperature and corrosive electrochemical cell environment. A melt of a alkali metal boride tetrafluoride salt including such as KF to lower its melting point is prepared including a dissolved boron containing material, for instance NiB, MnB.sub.2, or CrB.sub.2. A transition metal to be coated is immersed in the melt at a temperature of no more than 700.degree. C. and a surface boride layer of that transition metal is formed within a period of about 24 hours on the substrate surface.

  13. Method of boronizing transition-metal surfaces

    SciTech Connect

    Koyama, K.; Shimotake, H.

    1981-08-28

    A method is presented for preparing a boride layer on a transition metal substrate for use in corrosive environments or as a harden surface in machine applications. This method is particularly useful in treating current collectors for use within a high temperature and corrosive electrochemical cell environment. A melt of a alkali metal boride tetrafluoride salt including such as KF to lower its melting point is prepared including a dissolved boron containing material, for instance NiB, MnB/sub 2/, or CrB/sub 2/. A transition metal to be coated is immersed in the melt at a temperature of no more than 700/sup 0/C and a surface boride layer of that transition metal is formed within a period of about 24 hours on the substrate surface.

  14. The tuning of metal enhanced fluorescence for sensing applications.

    PubMed

    Ganguly, Mainak; Mondal, Chanchal; Chowdhury, Joydeep; Pal, Jaya; Pal, Anjali; Pal, Tarasankar

    2014-01-21

    Stable coinage metal nanoparticles (NPs) have been synthesized individually in an aqueous alkaline solution from the corresponding metal salts as precursors using the condensation product (CP) of salicylaldehyde and triethylenetetramine as a reagent. Silver and gold NPs are obtained with and without light illumination but UV irradiation is essential for Cu(0)NP formation. During nanoparticle formation the CP is oxidized to OCP which eventually becomes a fluorophore and also a stabilizer for the in situ produced NPs. It has been observed that silver and gold particle formation kinetics is accelerated by UV exposure. Thus the ease of evolution of coinage metal NP formation relates to their nobility. The as prepared OCP solutions containing coinage metals exhibit a fluorescence contrast behaviour (fluorescence enhancement by Cu and Ag; quenching by AuNP) due to the match and mismatch of wave vectors. The electric field evident from the FDTD simulation abreast of the scattering cross section of the NPs governed from Mie theory as a consequence of surface plasmon coupled emission (SPCE), near field electromagnetic intensity enhancement and lightening rod effect concentrating the electric field around the fluorophore are responsible for the Cu and AgNPs stimulated fluorescence. Again, lossy surface waves are anticipated for efficient quenching by the AuNPs. The most unprecedented observation is 'Turn On' fluorescence which is reported here as a result of the substitution of Au(0) or Cu(0) by Ag(0). Finally, the preferential fluorescence enhancement helps the selective detection of Ag(i) and Cu(ii) well below the US Environmental Protection Agency (EPA) permissible level by tuning the experimental conditions.

  15. Noble metal surface degradation induced by organothiols

    NASA Astrophysics Data System (ADS)

    de Poel, Wester; Gasseling, Anouk; Mulder, Peter; Steeghs, Antoon P. G.; Elemans, Johannes A. A. W.; van Enckevort, Willem J. P.; Rowan, Alan E.; Vlieg, Elias

    2017-08-01

    Copper, silver and gold layers evaporated on the muscovite mica (001) surface were exposed to a series of molecules containing an organothiol and/or a carboxylic acid chemical functional group to investigate the potential of these compounds to modify the surfaces. The surfaces were investigated using optical microscopy, atomic force microscopy, scanning electron microscopy, energy dispersive analysis of X-rays, and X-ray diffraction. Organothiols containing a carboxylic acid group were found to change the surface morphology drastically over a period of days, while molecules containing only one of these functional groups were usually not able to do so. The mechanism is most likely a reaction between the organothiol and the metal surface, forming a thermodynamically stable new compound. This finding could be of importance in the many applications where organothiols are used to functionalize noble metal surfaces.

  16. Rule for structures of open metal surfaces.

    PubMed

    Sun, Y Y; Xu, H; Feng, Y P; Huan, A C H; Wee, A T S

    2004-09-24

    We present a clear and simple rule for determining the relaxation sequences on open (stepped, vicinal, or high-Miller-index) metal surfaces. At the bulk-truncated configuration of a surface, a surface slab is defined where the coordination of atoms is reduced from the bulk. The rule predicts that the interlayer spacings within this slab contract, while the interlayer spacing between this slab and the substrate expands. By first-principles calculations, we show that this rule is obeyed on all open Cu surfaces with interlayer spacings down to about 0.5 A. We also illustrate a direct relation of the relaxation sequences to the charge redistribution on these surfaces, which is demonstrated to be driving the multilayer relaxations. The applicability of the rule can be extended to other fcc and bcc metals, including unreconstructed and missing-row surfaces.

  17. Nucleation rates for the condensation of monovalent metals

    NASA Astrophysics Data System (ADS)

    Bahadur, Ranjit; McClurg, Richard B.

    2004-12-01

    We show that consideration of both cluster growth and magic numbers are necessary to accurately calculate nucleation rates for the condensation of alkali and coinage metal vapors. The effects are not additive. Rates calculated using the modified theory differ up to several orders of magnitude from typical classical calculations. Calculated rates compare favorably with experimental nucleation onset and rate data for lithium, sodium, cesium, and silver. Verifiable predictions are made for the other alkali and coinage metals.

  18. Methods and compositions for boronizing metallic surfaces

    SciTech Connect

    Reid, D. K.

    1985-11-26

    The present disclosure is directed to methods and compositions for boronizing metal and in particular ferrous surfaces. It has been discovered that if hydrocarbons are processed in metallic equipment which have been previously boronized, that coke formation and deposition which is commonly experienced at high temperatures can be minimized if not totally eliminated. The compositions utilized for this purpose are comprised of boron or boron compounds contained in an organic solvent or carrier together with specific activating materials.

  19. Internal and surface phenomena in metal combustion

    NASA Technical Reports Server (NTRS)

    Dreizin, Edward L.; Molodetsky, Irina E.; Law, Chung K.

    1995-01-01

    Combustion of metals has been widely studied in the past, primarily because of their high oxidation enthalpies. A general understanding of metal combustion has been developed based on the recognition of the existence of both vapor-phase and surface reactions and involvement of the reaction products in the ensuing heterogeneous combustion. However, distinct features often observed in metal particle combustion, such as brightness oscillations and jumps (spearpoints), disruptive burning, and non-symmetric flames are not currently understood. Recent metal combustion experiments using uniform high-temperature metal droplets produced by a novel micro-arc technique have indicated that oxygen dissolves in the interior of burning particles of certain metals and that the subsequent transformations of the metal-oxygen solutions into stoichiometric oxides are accompanied with sufficient heat release to cause observed brightness and temperature jumps. Similar oxygen dissolution has been observed in recent experiments on bulk iron combustion but has not been associated with such dramatic effects. This research addresses heterogeneous metal droplet combustion, specifically focusing on oxygen penetration into the burning metal droplets, and its influence on the metal combustion rate, temperature history, and disruptive burning. A unique feature of the experimental approach is the combination of the microgravity environment with a novel micro-arc Generator of Monodispersed Metal Droplets (GEMMED), ensuring repeatable formation and ignition of uniform metal droplets with controllable initial temperature and velocity. The droplet initial temperatures can be adjusted within a wide range from just above the metal melting point, which provides means to ignite droplets instantly upon entering an oxygen containing environment. Initial droplet velocity will be set equal to zero allowing one to organize metal combustion microgravity experiments in a fashion similar to usual microgravity

  20. 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

  1. Atomic Manipulation on Metal Surfaces

    NASA Astrophysics Data System (ADS)

    Ternes, Markus; Lutz, Christopher P.; Heinrich, Andreas J.

    Half a century ago, Nobel Laureate Richard Feynman asked in a now-famous lecture what would happen if we could precisely position individual atoms at will [R.P. Feynman, Eng. Sci. 23, 22 (1960)]. This dream became a reality some 30 years later when Eigler and Schweizer were the first to position individual Xe atoms at will with the probe tip of a low-temperature scanning tunneling microscope (STM) on a Ni surface [D.M. Eigler, E.K. Schweizer, Nature 344, 524 (1990)].

  2. Method of coating metal surfaces to form protective metal coating thereon

    DOEpatents

    Krikorian, O.H.; Curtis, P.G.

    1992-03-31

    A process is disclosed for forming a protective metal coating on a metal surface using a flux consisting of an alkali metal fluoride, an alkaline earth metal fluoride, an alkali metal fluoaluminate, an alkali metal fluosilicate, and mixtures thereof. The flux, in particulate form, is mixed with particles of a metal coating material which may comprise aluminum, chromium, mixtures thereof, and alloys containing at least 50 wt. % aluminum and the particulate mixture is applied to the metal surface in a single step, followed by heating the coated metal surface to a temperature sufficient to cause the metal coating material to react with the metal surface to form a protective reaction product in the form of a metal coating bonded to the metal surface. The metal surface which reacts with the metal coating material to form the protective coating may comprise Fe, Co, Ni, Ti, V, Cr, Mn, Zr, Nb, Mo, Tc, Hf, Ta, W, Re and alloys thereof. 1 figure.

  3. Method of coating metal surfaces to form protective metal coating thereon

    DOEpatents

    Krikorian, Oscar H.; Curtis, Paul G.

    1992-01-01

    A process is disclosed for forming a protective metal coating on a metal surface using a flux consisting of an alkali metal fluoride, an alkaline earth metal fluoride, an alkali metal fluoaluminate, an alkali metal fluosilicate, and mixtures thereof. The flux, in particulate form, is mixed with particles of a metal coating material which may comprise aluminum, chromium, mixtures thereof, and alloys containing at least 50 wt. % aluminum and the particulate mixture is applied to the metal surface in a single step, followed by heating the coated metal surface to a temperature sufficient to cause the metal coating material to react with the metal surface to form a protective reaction product in the form of a metal coating bonded to the metal surface. The metal surface which reacts with the metal coating material to form the protective coating may comprise Fe, Co, Ni, Ti, V, Cr, Mn, Zr, Nb, Mo, Tc, Hf, Ta, W, Re and alloys thereof.

  4. Theory of Metal Surface Field Evaporation.

    NASA Astrophysics Data System (ADS)

    McMullen, Edward Richard

    This work addresses the effects of intense positive electric fields applied to two metal surfaces. In particular, the outward shifting of the surface layer in response to the fields, the redistribution of electronic charge within the metal initiated by the fields, and prediction of the minimum field strength which will produce evaporation of the surface monolayer of positive charge and attendant electrons are investigated. Density functional theory, a powerful method of treating the inhomogeneous electron gas, is the theoretical approach taken in this work. Its utility and success within the local density approximation have been proven for many systems, diverse in size and nature, including the metal surface. By positioning the surface monolayer at a particular separation measured along the surface normal and calculating the surface energy from the semi-self-consistent electronic density generated via the Schrodinger equation with a one -electron effective potential, and repeating the procedure for other separations, an energy-displacement curve for a particular applied field can be mapped. A minimum in the curve for fields less than the least required for field evaporation locates the equilibrium position of the surface layer. The minimum will just disappear for the critical field. In this way, the critical field for the uniform positive-background-charge metal, herein named sodium-jellium (NaJ), is found to be 1.8 V/(ANGSTROM); that for Al (lll) is found to be 4.5 V/(ANGSTROM). The zero-field energies for both metals are found to map onto a curve obtained from a universal binding energy expression. This expression, which scales according to two parameters which can be related to known empirical quantities, is extended by a simple method to predict the critical fields for surface layer evaporation of a range of metals. Comparison is made of the predicted values with experimentally available critical fields for field evaporating atoms/ions singly from rounded

  5. Terahertz NDE for metallic surface roughness evaluation

    NASA Astrophysics Data System (ADS)

    Anastasi, Robert F.; Madaras, Eric I.

    2006-03-01

    Metallic surface roughness in a nominally smooth surface is a potential indication of material degradation or damage. When the surface is coated or covered with an opaque dielectric material, such as paint or insulation, then inspecting for surface changes becomes almost impossible. Terahertz NDE is a method capable of penetrating the coating and inspecting the metallic surface. The terahertz frequency regime is between 100 GHz and 10 THz and has a free space wavelength of 300 micrometers at 1 THz. Pulsed terahertz radiation, can be generated and detected using optical excitation of biased semiconductors with femtosecond laser pulses. The resulting time domain signal is 320 picoseconds in duration. In this application, samples are inspected with a commercial terahertz NDE system that scans the sample and generates a set of time-domain signals that are a function of the signal reflected from the metallic surface. Post processing is then performed in the time and frequency domains to generate C-scan type images that show scattering effects due to surface non-uniformity.

  6. Terahertz NDE for Metallic Surface Roughness Evaluation

    NASA Technical Reports Server (NTRS)

    Madaras, Eric I.; Anastasi, Robert F.

    2006-01-01

    Metallic surface roughness in a nominally smooth surface is a potential indication of material degradation or damage. When the surface is coated or covered with an opaque dielectric material, such as paint or insulation, then inspecting for surface changes becomes almost impossible. Terahertz NDE is a method capable of penetrating the coating and inspecting the metallic surface. The terahertz frequency regime is between 100 GHz and 10 THz and has a free space wavelength of 300 micrometers at 1 THz. Pulsed terahertz radiation, can be generated and detected using optical excitation of biased semiconductors with femtosecond laser pulses. The resulting time domain signal is 320 picoseconds in duration. In this application, samples are inspected with a commercial terahertz NDE system that scans the sample and generates a set of time-domain signals that are a function of the backscatter from the metallic surface. Post processing is then performed in the time and frequency domains to generate C-scan type images that show scattering effects due to surface non-uniformity.

  7. Rigid multipodal platforms for metal surfaces

    PubMed Central

    Valášek, Michal; Lindner, Marcin

    2016-01-01

    Summary In this review the recent progress in molecular platforms that form rigid and well-defined contact to a metal surface are discussed. Most of the presented examples have at least three anchoring units in order to control the spatial arrangement of the protruding molecular subunit. Another interesting feature is the lateral orientation of these foot structures which, depending on the particular application, is equally important as the spatial arrangement of the molecules. The numerous approaches towards assembling and organizing functional molecules into specific architectures on metal substrates are reviewed here. Particular attention is paid to variations of both, the core structures and the anchoring groups. Furthermore, the analytical methods enabling the investigation of individual molecules as well as monomolecular layers of ordered platform structures are summarized. The presented multipodal platforms bearing several anchoring groups form considerably more stable molecule–metal contacts than corresponding monopodal analogues and exhibit an enlarged separation of the functional molecules due to the increased footprint, as well as restrict tilting of the functional termini with respect to the metal surface. These platforms are thus ideally suited to tune important properties of the molecule–metal interface. On a single-molecule level, several of these platforms enable the control over the arrangement of the protruding rod-type molecular structures (e.g., molecular wires, switches, rotors, sensors) with respect to the surface of the substrate. PMID:27335731

  8. Surface Plasmon Propagation in Nanostructured Metallic Waveguides

    NASA Astrophysics Data System (ADS)

    Calm, Y. M.; Merlo, J. M.; Rose, A. H.; Nesbitt, N. T.; Boyce, A. M.; McMahon, G.; Burns, M. J.; Kempa, K.; Naughton, M. J.

    2015-03-01

    Visible frequencies of light can be routed on subwavelength scales with nanostructured, metallic waveguides by coupling optical energy to surface plasmon (SP) modes at a metal-insulator interface. Epitaxially-grown Ag nanowires and nanocoaxes provide a low-loss, ``model'' system to characterize the propagation of SP waves. We have studied these structures by electron, focused ion, scanning probe, and optical microscopies, and have observed propagation lengths exceeding 15λvac with confinement on the order of 0 . 07(λvac) 2 . Experimental efforts towards lithographically-fabricated metal-insulator-metal waveguides are discussed. Finally, an architecture for a nanocoax-based optical microscope, which extracts near-field (evanescent) information and propagates it into the far-field, is presented. Supported by the W.M. Keck Foundation.

  9. Surface energy of metal alloy nanoparticles

    NASA Astrophysics Data System (ADS)

    Takrori, Fahed M.; Ayyad, Ahmed

    2017-04-01

    The measurement of surface energy of alloy nanoparticles experimentally is still a challenge therefore theoretical work is necessary to estimate its value. In continuation of our previous work on the calculation of the surface energy of pure metallic nanoparticles we have extended our work to calculate the surface energy of different alloy systems, namely, Co-Ni, Au-Cu, Cu-Al, Cu-Mg and Mo-Cs binary alloys. It is shown that the surface energy of metallic binary alloy decreases with decreasing particle size approaching relatively small values at small sizes. When both metals in the alloy obey the Hume-Rothery rules, the difference in the surface energy is small at the macroscopic as well as in the nano-scale. However when the alloy deviated from these rules the difference in surface energy is large in the macroscopic and in the nano scales. Interestingly when solid solution formation is not possible at the macroscopic scale according to the Hume-Rothery rules, it is shown it may form at the nano-scale. To our knowledge these findings here are presented for the first time and is challenging from fundamental as well as technological point of views.

  10. Surface studies of gas sensing metal oxides.

    PubMed

    Batzill, Matthias; Diebold, Ulrike

    2007-05-21

    The relation of surface science studies of single crystal metal oxides to gas sensing applications is reviewed. Most metal oxide gas sensors are used to detect oxidizing or reducing gases and therefore this article focuses on surface reduction processes and the interaction of oxygen with these surfaces. The systems that are discussed are: (i) the oxygen vacancy formation on the surface of the ion conductor CeO(2)(111); (ii) interaction of oxygen with TiO(2) (both adsorption processes and the incorporation of oxygen into the TiO(2)(110) lattice are discussed); (iii) the varying surface composition of SnO(2)(101) and its consequence for the adsorption of water; and (iv) Cu modified ZnO(0001)-Zn surfaces and its interaction with oxygen. These examples are chosen to give a comprehensive overview of surface science studies of different kinds of gas sensing materials and to illustrate the potential that surface science studies have to give fundamental insight into gas sensing phenomena.

  11. Excimer laser irradiation of metal surfaces

    NASA Astrophysics Data System (ADS)

    Kinsman, Grant

    In this work a new method of enhancing CO2 laser processing by modifying the radiative properties of a metal surface is studied. In this procedure, an excimer laser (XeCl) or KrF) exposes the metal surface to overlapping pulses of high intensity, 10(exp 8) - 10(exp 9) W cm(exp -2), and short pulse duration, 30 nsec FWHM (Full Width Half Maximum), to promote structural and chemical change. The major processing effect at these intensities is the production of a surface plasma which can lead to the formation of a laser supported detonation wave (LSD wave). This shock wave can interact with the thin molten layer on the metal surface influencing to a varying degree surface oxidation and roughness features. The possibility of the expulsion, oxidation and redeposition of molten droplets, leading to the formation of micron thick oxide layers, is related to bulk metal properties and the incident laser intensity. A correlation is found between the expulsion of molten droplets and a Reynolds number, showing the interaction is turbulent. The permanent effects of these interactions on metal surfaces are observed through scanning electron microscopy (SEM), transient calorimetric measurements and Fourier transform infrared (FTIR) spectroscopy. Observed surface textures are related to the scanning procedures used to irradiate the metal surface. Fundamental radiative properties of a metal surface, the total hemispherical emissivity, the near-normal spectral absorptivity, and others are examined in this study as they are affected by excimer laser radiation. It is determined that for heavily exposed Al surface, alpha' (10.6 microns) can be increased to values close to unity. Data relating to material removal rates and chemical surface modification for excimer laser radiation is also discussed. The resultant reduction in the near-normal reflectivity solves the fundamental problem of coupling laser radiation into highly reflective and conductive metals such as copper and aluminum. The

  12. RF Breakdown of Metallic Surfaces in Hydrogen

    SciTech Connect

    BastaniNejad, M.; Elmustafa, A.A.; Yonehara, K.; Chung, M.; Jansson, A.; Hu, M.; Moretti, A.; Popovic, M.; Alsharo'a, M.; Neubauer, M.; Sah, R.; /Muons Inc., Batavia

    2009-05-01

    In earlier reports, microscopic images of the surfaces of metallic electrodes used in high-pressure gas-filled 805 MHz RF cavity experiments were used to investigate the mechanism of RF breakdown of tungsten, molybdenum, and beryllium electrode surfaces. Plots of remnants were consistent with the breakdown events being due to field emission, due to the quantum mechanical tunnelling of electrons through a barrier as described by Fowler and Nordheim. In the work described here, these studies have been extended to include tin, aluminium, and copper. Contamination of the surfaces, discovered after the experiments concluded, have cast some doubt on the proper qualities to assign to the metallic surfaces. However, two significant results are noted. First, the maximum stable RF gradient of contaminated copper electrodes is higher than for a clean surface. Second, the addition of as little as 0.01% of SF6 to the hydrogen gas increased the maximum stable gradient, which implies that models of RF breakdown in hydrogen gas will be important to the study of metallic breakdown.

  13. Continuous metal plasmonic frequency selective surfaces.

    PubMed

    Zhang, Jianfa; Ou, Jun-Yu; Papasimakis, Nikitas; Chen, Yifang; Macdonald, Kevin F; Zheludev, Nikolay I

    2011-11-07

    In the microwave part of the spectrum, where losses are minimal, metal films regularly patterned (perforated) on the sub-wavelength scale achieve spectral selectivity by balancing the transmission and reflection characteristics of the surface. Here we show for optical frequencies, where joule losses are important, that periodic structuring of a metal film without violation of continuity (i.e. without perforation) is sufficient to achieve substantial modification of reflectivity. By engineering the geometry of the structure imposed on a surface one can dramatically change the perceived color of the metal without employing any form of chemical modification, thin-film coating or diffraction effects. This novel frequency selective effect is underpinned by plasmonic Joule losses in the constituent elements of the patterns (dubbed 'intaglio' and 'bas relief' metamaterials to distinguish indented and raised structures respectively) and is specific to the optical part of the spectrum. It has the advantage of maintaining the integrity of metal surfaces and is well suited to high-throughput fabrication via techniques such as nano-imprint.

  14. Metallic surface states in elemental electrides

    NASA Astrophysics Data System (ADS)

    Naumov, Ivan I.; Hemley, Russell J.

    2017-07-01

    Recent high-pressure studies have uncovered an alternative class of materials, insulating electride phases created by compression of simple metals. These exotic insulating phases develop an unusual electronic structure: the valence electrons move away from the nuclei and condense at interstitial sites, thereby acquiring the role of atomic anions or even molecules. We show that they are also topological phases as they exhibit a wide diversity of metallic surface states (SSs) that are controlled by the bulk electronic structure. The electronic reconstruction occurs that involves charge transfer between the surfaces of opposite polarity making both of them metallic, resembling the appearance of the two-dimensional gas at the renowned SrTi O3 /LaAl O3 interface. Remarkably, these materials thus embody seemingly disparate physical concepts—chemical electron localization, topological control of bulk-surface conductivity, and the two-dimensional electron gas. Such metallic SSs could be probed by direct electrical resistance or by standard photoemission measurements on recovery to ambient conditions.

  15. The Surface Chemistry of Metal Chalcogenide Nanocrystals

    NASA Astrophysics Data System (ADS)

    Anderson, Nicholas Charles

    The surface chemistry of metal chalcogenide nanocrystals is explored through several interrelated analytical investigations. After a brief discussion of the nanocrystal history and applications, molecular orbital theory is used to describe the electronic properties of semiconductors, and how these materials behave on the nanoscale. Quantum confinement plays a major role in dictating the optical properties of metal chalcogenide nanocrystals, however surface states also have an equally significant contribution to the electronic properties of nanocrystals due to the high surface area to volume ratio of nanoscale semiconductors. Controlling surface chemistry is essential to functionalizing these materials for biological imaging and photovoltaic device applications. To better understand the surface chemistry of semiconducting nanocrystals, three competing surface chemistry models are presented: 1.) The TOPO model, 2.) the Non-stoichiometric model, and 3.) the Neutral Fragment model. Both the non-stoichiometric and neutral fragment models accurately describe the behavior of metal chalcogenide nanocrystals. These models rely on the covalent bond classification system, which divides ligands into three classes: 1.) X-type, 1-electron donating ligands that balance charge with excess metal at the nanocrystal surface, 2.) L-type, 2-electron donors that bind metal sites, and 3.) Z-type, 2-electron acceptors that bind chalcogenide sites. Each of these ligand classes is explored in detail to better understand the surface chemistry of metal chalcogenide nanocrystals. First, chloride-terminated, tri-n-butylphosphine (Bu 3P) bound CdSe nanocrystals were prepared by cleaving carboxylate ligands from CdSe nanocrystals with chlorotrimethylsilane in Bu3P solution. 1H and 31P{1H} nuclear magnetic resonance spectra of the isolated nanocrystals allowed assignment of distinct signals from several free and bound species, including surface-bound Bu3P and [Bu3P-H]+[Cl]- ligands as well as a Bu

  16. Process Of Bonding A Metal Brush Structure To A Planar Surface Of A Metal Substrate

    DOEpatents

    Slattery, Kevin T.; Driemeyer, Daniel E.; Wille; Gerald W.

    1999-11-02

    Process for bonding a metal brush structure to a planar surface of a metal substrate in which an array of metal rods are retained and immobilized at their tips by a common retention layer formed of metal, and the brush structure is then joined to a planar surface of a metal substrate via the retention layer.

  17. Surface plasmon resonances in liquid metal nanoparticles

    NASA Astrophysics Data System (ADS)

    Ershov, A. E.; Gerasimov, V. S.; Gavrilyuk, A. P.; Karpov, S. V.

    2017-06-01

    We have shown significant suppression of resonant properties of metallic nanoparticles at the surface plasmon frequency during the phase transition "solid-liquid" in the basic materials of nanoplasmonics (Ag, Au). Using experimental values of the optical constants of liquid and solid metals, we have calculated nanoparticle plasmonic absorption spectra. The effect was demonstrated for single particles, dimers and trimers, as well as for the large multiparticle colloidal aggregates. Experimental verification was performed for single Au nanoparticles heated to the melting temperature and above up to full suppression of the surface plasmon resonance. It is emphasized that this effect may underlie the nonlinear optical response of composite materials containing plasmonic nanoparticles and their aggregates.

  18. Ambient pressure photoemission spectroscopy of metal surfaces

    NASA Astrophysics Data System (ADS)

    Baikie, Iain D.; Grain, Angela C.; Sutherland, James; Law, Jamie

    2014-12-01

    We describe a novel photoemission technique utilizing a traditional Kelvin probe as a detector of electrons/atmospheric ions ejected from metallic surfaces (Au, Ag, Cu, Fe, Ni, Ti, Zn, Al) illuminated by a deep ultra-violet (DUV) source under ambient pressure. To surmount the limitation of electron scattering in air the incident photon energy is rastered rather than applying a variable retarding electric field as is used with UPS. This arrangement can be applied in several operational modes: using the DUV source to determine the photoemission threshold (Φ) with 30-50 meV resolution and also the Kelvin probe, under dark conditions, to measure contact potential difference (CPD) between the Kelvin probe tip and the metallic sample with an accuracy of 1-3 meV. We have studied the relationship between the photoelectric threshold and CPD of metal surfaces cleaned in ambient conditions. Inclusion of a second spectroscopic visible source was used to confirm a semiconducting oxide, possibly Cu2O, via surface photovoltage measurements with the KP. This dual detection system can be easily extended to controlled gas conditions, relative humidity control and sample heating/cooling.

  19. Surface plasmon polaritons in artificial metallic nanostructures

    NASA Astrophysics Data System (ADS)

    Briscoe, Jayson Lawrence

    Surface plasmon polaritons have been the focus of intense research due to their many unique properties such as high electromagnetic field localization, extreme sensitivity to surface conditions, and subwavelength confinement of electromagnetic waves. The area of potential impact is vast and includes promising advancements in photonic circuits, high speed photodetection, hyperspectral imaging, spectroscopy, enhanced solar cells, ultra-small scale lithography, and microscopy. My research has focused on utilizing these properties to design and demonstrate new phenomena and implement real-world applications using artificial metallic nanostructures. Artificial metallic nanostructures employed during my research begin as thin planar gold films which are then lithographically patterned according to previously determined dimensions. The result is a nanopatterned device which can excite surface plasmon polaritons on its surface under specific conditions. Through my research I characterized the optical properties of these devices for further insight into the interesting properties of surface plasmon polaritons. Exploration of these properties led to advancements in biosensing, development of artificial media to enhance and control light-matter interactions at the nanoscale, and hybrid plasmonic cavities. Demonstrations from these advancements include: label-free immunosensing of Plasmodium in a whole blood lysate, low part-per-trillion detection of microcystin-LR, enhanced refractive index sensitivity of novel resonant plasmonic devices, a defect-based plasmonic crystal, spontaneous emission modification of colloidal quantum dots, and coupling of plasmonic and optical Fabry-Perot resonant modes in a hybrid cavity.

  20. METHOD OF FORMING A PROTECTIVE COATING ON FERROUS METAL SURFACES

    DOEpatents

    Schweitzer, D.G.; Weeks, J.R.; Kammerer, O.F.; Gurinsky, D.H.

    1960-02-23

    A method is described of protecting ferrous metal surfaces from corrosive attack by liquid metals, such as liquid bismuth or lead-bismuth alloys. The nitrogen content of the ferrous metal surface is first reduced by reacting the metal surface with a metal which forms a stable nitride. Thereafter, the surface is contacted with liquid metal containing at least 2 ppm zirconium at a temperature in the range of 550 to 1100 deg C to form an adherent zirconium carbide layer on the ferrous surface.

  1. Method for preparing hydride configurations and reactive metal surfaces

    DOEpatents

    Silver, G.L.

    1984-05-18

    A method for preparing reactive metal surfaces, particularly uranium surfaces is disclosed, whereby the metal is immediately reactive to hydrogen gas at room temperature and low pressure. The metal surfaces are first pretreated by exposure to an acid which forms an adherent hydride-bearing composition on the metal surface. Subsequent heating of the pretreated metal at a temperature sufficient to decompose the hydride coating in vacuum or inert gas renders the metal surface instantaneously reactive to hydrogen gas at room temperature and low pressure.

  2. 75 FR 1684 - Notification of Citizens Coinage Advisory Committee January 2010 Public Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-01-12

    ... Gettysburg National Military Park, Glacier National Park, Olympic National Park, Vicksburg National Military Park, and Chickasaw National Recreation Area. Interested persons should call 202-354-7502 for the... Secretary of the Treasury on any theme or design proposals relating to circulating coinage, bullion...

  3. 76 FR 44400 - Notification of Citizens Coinage Advisory Committee July 26, 2011 Public Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-07-25

    ... United States Mint Notification of Citizens Coinage Advisory Committee July 26, 2011 Public Meeting...: Pursuant to United States Code, Title 31, section 5135(b)(8)(C), the United States Mint announces the.... Time: 9 a.m. to 1 p.m. Location: United States Mint, 801 9th Street, NW., Washington, DC,...

  4. 77 FR 35480 - Notification of Citizens Coinage Advisory Committee June 26, 2012, Public Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-13

    ... United States Mint Notification of Citizens Coinage Advisory Committee June 26, 2012, Public Meeting...: Pursuant to United States Code, Title 31, section 5135(b)(8)(C), the United States Mint announces the.... Time: 9:00 a.m. to 2:00 p.m. Location: 8th Floor Board Room, United States Mint, 801 9th Street...

  5. 78 FR 42592 - Notification of Citizens Coinage Advisory Committee July 23 and 24, 2013, Public Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-07-16

    ... United States Mint Notification of Citizens Coinage Advisory Committee July 23 and 24, 2013, Public.... SUMMARY: Pursuant to United States Code, Title 31, section 5135(b)(8)(C), the United States Mint announces.... Location: Conference Room A, United States Mint, 801 9th Street NW., Washington, DC 20220. Subject:...

  6. 75 FR 13344 - Revised Meeting Time for Citizens Coinage Advisory Committee March 2010 Public Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-19

    ... United States Mint Revised Meeting Time for Citizens Coinage Advisory Committee March 2010 Public Meeting AGENCY: United States Mint, Department of the Treasury. ACTION: Notification. SUMMARY: Pursuant to United States Code, Title 31, section 5135(b)(8)(C), the United States Mint announces the Citizens...

  7. 76 FR 24959 - Notification of Citizens Coinage Advisory Committee, Public Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-05-03

    ... United States Mint Notification of Citizens Coinage Advisory Committee, Public Meeting ACTION: Notice. SUMMARY: Pursuant to United States Code, Title 31, section 5135(b)(8)(C), the United States Mint announces..., 2011. Time: 9 a.m. to 1 p.m. Location: Conference Room A, United States Mint, 801 9th Street,...

  8. 75 FR 11228 - Citizens Coinage Advisory Committee March 2010 Public Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-10

    ... United States Mint Citizens Coinage Advisory Committee March 2010 Public Meeting AGENCY: United States... (CCAC) public meeting scheduled for March 23, 2010. Date: March 23, 2010. Time: 3 p.m. to 5 p.m...(b)(8)(C). Dated: March 5, 2010. Edmund C. Moy, Director, United States Mint. BILLING CODE P ...

  9. 75 FR 62184 - Notification of Citizens Coinage Advisory Committee October 26, 2010 Public Meeting

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-10-07

    ... 2012 America the Beautiful Quarter-Dollar Coins, designs for the Arnold Palmer Congressional Gold Medal, and designs for the New Frontier Congressional Gold Medal. Interested persons should call 202-354-6700..., bullion coinage, Congressional Gold Medals, and national and other medals. Advises the Secretary of...

  10. Ion neutralization at metal surfaces by surface-plasmon excitation

    SciTech Connect

    Almulhem, A.A.

    1988-01-01

    Electron capture by ions scattered from metal surfaces is usually assumed to occur via resonance tunneling or Auger neutralization. A new mechanism is proposed, wherein a surface plasmon is excited during the electron capture. The Fock-Tani transformation is used to transform the Hamiltonian into a form which explicitly contains a term that corresponds to this process. Using this term, the matrix elements are calculated analytically and used to evaluate the transition rate as a function of distance from the surface. Since this is a rearrangement process, the matrix element contains an orthogonalization term. The theory is applied to the scattering of protons from an aluminum surface in which the proton captures an electron into the 1s state. From the results obtained for the transition rate and neutral fractions, it is concluded that this process is important, at least in the low energy region. When the calculations are done with the orthogonalization term in the matrix element neglected, the transition rate and neutral fraction increased appreciably. This shows the importance of this term, and implies that it cannot be neglected as was done in other theories of neutralization at metal surfaces.

  11. Metallic surfaces decontamination by using laser light

    SciTech Connect

    Moggia, Fabrice; Lecardonnel, Xavier

    2013-07-01

    Metal surface cleaning appears to be one of the major priorities for industries especially for nuclear industries. The research and the development of a new technology that is able to meet the actual requirements (i.e. waste volume minimization, liquid effluents and chemicals free process...) seems to be the main commitment. Currently, a wide panel of technologies already exists (e.g. blasting, disk sander, electro-decontamination...) but for some of them, the efficiency is limited (e.g, Dry Ice blasting) and for others, the wastes production (liquid and/or solid) remains an important issue. One answer could be the use of a LASER light process. Since a couple of years, the Clean- Up Business Unit of the AREVA group investigates this decontamination technology. Many tests have been already performed in inactive (i.e. on simulants such as paints, inks, resins, metallic oxides) or active conditions (i.e. pieces covered with a thick metallic oxide layer and metallic pieces covered with grease). The paper will describe the results obtained in term of decontamination efficiency during all our validation process. Metallographic characterizations (i.e. SEM, X-ray scattering) and radiological analysis will be provided. We will also focus our paper on the future deployment of the LASER technology and its commercial use at La Hague reprocessing facility in 2013. (authors)

  12. Microwave properties of thermochromic metal oxide surfaces

    NASA Astrophysics Data System (ADS)

    Ousbäck, Jan-Olof; Kariis, Hans

    2006-09-01

    Thermochromic metal oxides with a Mott transition, such as vanadium dioxide (VO II) exhibit an extensive alteration in their infrared reflectivity when heated above the transition temperature. For VO II the infrared reflectivity increases as the material becomes more metal-like above the transition temperature at 68°C. Given these dynamic electromagnetic properties in the IR-range, it is interesting to study the reflection of the material also in other wavelength ranges. The microwave properties of VO II as a function of temperature have been investigated here. Measurements were made with an automated network analyzer combined with an electrical heating unit. Reflection properties of VO II in the microwave region were determined. Above the transition temperature, an increase in the reflection of the surface was observed. The VO II became more metal-like in the whole measured microwave frequency range, as in the infrared region. It is concluded that VO II not only can be used to adapt the thermal emissivity of a surface but also to control the microwave reflectivity. Possible applications are switchable radomes, switchable radarabsorbers and heat protection for antenna apertures.

  13. Modeling surface roughness scattering in metallic nanowires

    SciTech Connect

    Moors, Kristof; Sorée, Bart; Magnus, Wim

    2015-09-28

    Ando's model provides a rigorous quantum-mechanical framework for electron-surface roughness scattering, based on the detailed roughness structure. We apply this method to metallic nanowires and improve the model introducing surface roughness distribution functions on a finite domain with analytical expressions for the average surface roughness matrix elements. This approach is valid for any roughness size and extends beyond the commonly used Prange-Nee approximation. The resistivity scaling is obtained from the self-consistent relaxation time solution of the Boltzmann transport equation and is compared to Prange-Nee's approach and other known methods. The results show that a substantial drop in resistivity can be obtained for certain diameters by achieving a large momentum gap between Fermi level states with positive and negative momentum in the transport direction.

  14. Adsorption of pentacene on (100) vicinal surfaces: role of coordination, surface chemistry and vdWs effects

    NASA Astrophysics Data System (ADS)

    Matos, Jeronimo; Kara, Abdelkader

    2015-03-01

    In contrast to low miller index surfaces, vicinal surfaces are characterized by steps and step edges that not only present an interesting atomic landscape for the adsorption organic molecules, but also a unique electronic structure resulting in part from the low coordinated atoms at the step edges. The adsorption of pentacene on the stepped (511), (711), (911) surfaces (respectively 3, 4 and 5-atom wide terraces) of Cu and Ag (coinage transition metals); Pt (reactive transition metal); and Ni (reactive, magnetic transition metal) are studied using density functional theory, in order to investigate the support effects arising from differing surface chemistry. We compare the adsorption energy, adsorption geometry and electronic structure predicted by the PBE functional with those obtained from one of the optimized vdW-DF methods: optB88-vdW. Work supported by the U.S. Department of Energy Basic Energy Science under Contract No. DE-FG02-11ER16243.

  15. Nanoscopy Reveals Surface-Metallic Black Phosphorus

    NASA Astrophysics Data System (ADS)

    Abate, Yohannes

    Nanolayer and two-dimensional (2D) materials............. 1 such as graphene... 2,3 , boron nitride... 1,4 , transition metal dichalcogenides... 1 , 5 - 8 (TMDCs), and black phosphorus (BP)... 1 , 9 - 13 have intriguing fundamental physical properties and bear promise of important applications in electronics and optics... 9 , 14 , 15 . Of them, BP... 11 , 12 , 16 is a novel layered material that has been theoretically predicted... 10 to acquire plasmonic behavior for frequencies below ~0.4 eV when highly doped. The electronic properties of BP are unique due to its anisotropic structure . Advantages of BP as a material for nanoelectronics and nanooptics are due to the fact that, in contrast to metals, the free carrier density in it can be dynamically controlled by chemical or electrostatic gating, which has been demonstrated by its use in field-effect transistors.... 9 , 14 , 15 Despite all the interest that BP attracts, near-field and plasmonic properties of BP have not yet been investigated experimentally. Here we report the first observation of nanoscopic near-field properties of BP. We have discovered near-field patterns of outside bright fringes and high surface polarizability of nanofilm BP consistent with its surface-metallic, plasmonic behavior at mid-infrared (mid-IR) frequencies below critical frequency ωm ~ 1176 cm -1 . This has allowed us to estimate plasma frequency ωp ~ 0 . 4 eV, carrier density n ~ 1 . 1 × 1011 nm-1 and the thickness of the surface metallic layer of ~ 1 nm . We have also observed similar behavior in other nanolayer semiconductors such as TMDC MoS 2 and topological insulator Bi 2 Te 3 but not in insulators such as boron nitride. This new phenomenon is attributed to surface band-bending and charging of the semiconductor nanofilms. The surface plasmonic behavior has been found for 10-40 nm BP thickness but absent for 4 nm BP thickness. This discovery opens up a new field of research and potential applications in nanoelectronics

  16. Enantioselective recognition at mesoporous chiral metal surfaces

    PubMed Central

    Wattanakit, Chularat; Côme, Yémima Bon Saint; Lapeyre, Veronique; Bopp, Philippe A.; Heim, Matthias; Yadnum, Sudarat; Nokbin, Somkiat; Warakulwit, Chompunuch; Limtrakul, Jumras; Kuhn, Alexander

    2014-01-01

    Chirality is widespread in natural systems, and artificial reproduction of chiral recognition is a major scientific challenge, especially owing to various potential applications ranging from catalysis to sensing and separation science. In this context, molecular imprinting is a well-known approach for generating materials with enantioselective properties, and it has been successfully employed using polymers. However, it is particularly difficult to synthesize chiral metal matrices by this method. Here we report the fabrication of a chirally imprinted mesoporous metal, obtained by the electrochemical reduction of platinum salts in the presence of a liquid crystal phase and chiral template molecules. The porous platinum retains a chiral character after removal of the template molecules. A matrix obtained in this way exhibits a large active surface area due to its mesoporosity, and also shows a significant discrimination between two enantiomers, when they are probed using such materials as electrodes. PMID:24548992

  17. Enantioselective recognition at mesoporous chiral metal surfaces

    NASA Astrophysics Data System (ADS)

    Wattanakit, Chularat; Côme, Yémima Bon Saint; Lapeyre, Veronique; Bopp, Philippe A.; Heim, Matthias; Yadnum, Sudarat; Nokbin, Somkiat; Warakulwit, Chompunuch; Limtrakul, Jumras; Kuhn, Alexander

    2014-02-01

    Chirality is widespread in natural systems, and artificial reproduction of chiral recognition is a major scientific challenge, especially owing to various potential applications ranging from catalysis to sensing and separation science. In this context, molecular imprinting is a well-known approach for generating materials with enantioselective properties, and it has been successfully employed using polymers. However, it is particularly difficult to synthesize chiral metal matrices by this method. Here we report the fabrication of a chirally imprinted mesoporous metal, obtained by the electrochemical reduction of platinum salts in the presence of a liquid crystal phase and chiral template molecules. The porous platinum retains a chiral character after removal of the template molecules. A matrix obtained in this way exhibits a large active surface area due to its mesoporosity, and also shows a significant discrimination between two enantiomers, when they are probed using such materials as electrodes.

  18. Surface Dynamics and Roughening in Metal Nanowires

    NASA Astrophysics Data System (ADS)

    Zhang, C. H.; Stafford, C. A.; Goldstein, R. E.; Kassubek, F.

    2002-03-01

    Surface phonons and surface self-diffusion of atoms in metal nanowires are investigated in a continuum approach (jellium model). Electron-shell effects in such a system lead to islands of stability: regions in the (R_0,T) plane where arbitrarily long wires are stable with respect to small perturbations, R0 being the mean radius of the wire and T the temperature. We find that inertial dynamics always dominate over diffusion as one approaches the stability boundary. On the stability boundary, the surface of the nanowire becomes rough at any finite temperature, but remains smooth at T=0. The critical exponents describing this roughening transition are different than those for two-dimensional surfaces, due to the different dispersion relation for surface waves. We also find a novel reentrant roughening transition: for certain ranges of R_0, nanowires are stable within a temperature interval T_c1surfaces roughen exponentially, dominated by the maximum instability mode q_m, and finally will be trapped into a state with a permanent deformation if qm R_0>1. Research supported in part by NSF grant DMR0072703 and by an award from Research Corporation.

  19. Metal surface nitriding by laser induced plasma

    NASA Astrophysics Data System (ADS)

    Thomann, A. L.; Boulmer-Leborgne, C.; Andreazza-Vignolle, C.; Andreazza, P.; Hermann, J.; Blondiaux, G.

    1996-10-01

    We study a nitriding technique of metals by means of laser induced plasma. The synthesized layers are composed of a nitrogen concentration gradient over several μm depth, and are expected to be useful for tribological applications with no adhesion problem. The nitriding method is tested on the synthesis of titanium nitride which is a well-known compound, obtained at present by many deposition and diffusion techniques. In the method of interest, a laser beam is focused on a titanium target in a nitrogen atmosphere, leading to the creation of a plasma over the metal surface. In order to understand the layer formation, it is necessary to characterize the plasma as well as the surface that it has been in contact with. Progressive nitrogen incorporation in the titanium lattice and TiN synthesis are studied by characterizing samples prepared with increasing laser shot number (100-4000). The role of the laser wavelength is also inspected by comparing layers obtained with two kinds of pulsed lasers: a transversal-excited-atmospheric-pressure-CO2 laser (λ=10.6 μm) and a XeCl excimer laser (λ=308 nm). Simulations of the target temperature rise under laser irradiation are performed, which evidence differences in the initial laser/material interaction (material heated thickness, heating time duration, etc.) depending on the laser features (wavelength and pulse time duration). Results from plasma characterization also point out that the plasma composition and propagation mode depend on the laser wavelength. Correlation of these results with those obtained from layer analyses shows at first the important role played by the plasma in the nitrogen incorporation. Its presence is necessary and allows N2 dissociation and a better energy coupling with the target. Second, it appears that the nitrogen diffusion governs the nitriding process. The study of the metal nitriding efficiency, depending on the laser used, allows us to explain the differences observed in the layer features

  20. Ultra-fast boriding of metal surfaces for improved properties

    SciTech Connect

    Timur, Servet; Kartal, Guldem; Eryilmaz, Osman L.; Erdemir, Ali

    2015-02-10

    A method of ultra-fast boriding of a metal surface. The method includes the step of providing a metal component, providing a molten electrolyte having boron components therein, providing an electrochemical boriding system including an induction furnace, operating the induction furnace to establish a high temperature for the molten electrolyte, and boriding the metal surface to achieve a boride layer on the metal surface.

  1. Modification of surface properties of copper-refractory metal alloys

    DOEpatents

    Verhoeven, J.D.; Gibson, E.D.

    1993-10-12

    The surface properties of copper-refractory metal (CU-RF) alloy bodies are modified by heat treatments which cause the refractory metal to form a coating on the exterior surfaces of the alloy body. The alloys have a copper matrix with particles or dendrites of the refractory metal dispersed therein, which may be niobium, vanadium, tantalum, chromium, molybdenum, or tungsten. The surface properties of the bodies are changed from those of copper to that of the refractory metal.

  2. Paper surfaces for metal nanoparticle inkjet printing

    NASA Astrophysics Data System (ADS)

    Öhlund, Thomas; Örtegren, Jonas; Forsberg, Sven; Nilsson, Hans-Erik

    2012-10-01

    The widespread usage of paper and board offer largely unexploited possibilities for printed electronics applications. Reliability and performance of printed devices on comparatively rough and inhomogenous surfaces of paper does however pose challenges. Silver nanoparticle ink has been deposited on ten various paper substrates by inkjet printing. The papers are commercially available, and selected over a range of different types and construction. A smooth nonporous polyimide film was included as a nonporous reference substrate. The substrates have been characterized in terms of porosity, absorption rate, apparent surface energy, surface roughness and material content. The electrical conductivity of the resulting printed films have been measured after drying at 60 °C and again after additional curing at 110 °C. A qualitative analysis of the conductivity differences on the different substrates based on surface characterization and SEM examination is presented. Measurable parameters of importance to the final conductivity are pointed out, some of which are crucial to achieve conductivity. When certain criteria of the surfaces are met, paper media can be used as low cost, but comparably high performance substrates for metal nanoparticle inks in printed electronics applications.

  3. Photofield Emission Study of Metal Surfaces

    NASA Astrophysics Data System (ADS)

    Gao, Yongli

    In this thesis the efforts made to better understand the mech- anisms and to refine the apparatus of photofield emission are described. Photofield electron yield and photofield emission from surface electronic have been measured. Both demonstrate the surface sensitivity of this new technique. Analyses of laser-induced thermal effects are also reported which allows the simultaneous determination of both the temperature and workfunction of a laser illuminated surface as small as 50(ANGSTROM) in spatial extent. Theoretical calculations of photofield emission based on the relativistic elec- tronic band structure of tungsten are also carried out and the results are compared to experiment. Data from W(110) and W(111) for a number of different photon energies between 2.41eV and 3.54eV are reported. The measured yield is compared to the theoretical models of the photoexcitation process. Based on this comparison, it is concluded that the spatial variation of the vector potential (')A near the metal-vacuum interface is the dominant excitation mechanism in producing the photocurrent from a laser illuminated field emission tip. Photofield emission from surface electronic states is a unique probe to examine the radiation field near the vicinity of a metal sur- face since the surface states are localized within the first atomic layer of the surface. Studies of photofield emission from surface states on W(100), Mo(100) and Ir(111) are presented in the text. Data analysis shows that photofield emission from localized sur- face states depends predominantly on the normal component of the vector potential (')A. Laser-induced thermal effects on various surfaces of tungsten and molybdenum have been studied using field emitted electrons. Energy distributions measured by a dispersive electron energy ana- lyzer allow the temperature increase of a laser-illuminated surface to be determined to within (+OR-)10 K. In addition to estimating the tem - perature rise, small temperature

  4. Nano-donuts on metal surfaces

    NASA Astrophysics Data System (ADS)

    Rai, Abhishek; Nayak, Jayita; Roy Barman, Sudipta

    2015-03-01

    Nano-structures comprising of a pit surrounded by a circular ridge that resemble nano-donuts have been observed on flat terraces of both Au(1 1 1) and Al(1 0 0) surfaces after low energy (1.5-2 keV) rare gas (rg) ion implantation. From time lapse scanning tunneling microscopy, we demonstrate that these donuts originate from the rg bubbles that migrate out from the sub-surface region. The circular shape of the donuts is observed for both Ar and Ne bubbles. The donuts and the related nano-structures represent different stages of large time scale co-operative relaxation of Au atoms by long range elastic interaction after the rg bubbles leave the metal.

  5. Stabilizing the surface of lithium metal

    SciTech Connect

    Vaughey, J. T.; Liu, Gao; Zhang, Ji-Guang

    2014-05-01

    Lithium metal is an ideal anode for the next generation of high capacity rechargeable batteries, including Li-air, Li-S, and other Li-based batteries using intercalation compounds. To enable the broad applications for lithium anodes, more fundamental studies need to be conducted to simultaneously address the two barriers discussed above. One of the key breakthroughs in this field may come from the development of new electrolytes (and additives) which can form a stable SEI layer with enough mechanical strength and flexibility. The ideal electrolyte may consist of only two components; one component inhibits dendrite growth, while another component forms a stable SEI layer to improve Coulombic efficiency. In this review, the status of three approaches at manipulating and controlling the lithium metal – electrolyte interface were discussed. While previous studies concentrated on coatings with minimal surface connectivity, the approaches discussed, namely a coating that forms and dissipates into the electrolyte based on charge density, a coating bonded to the termination layer of lithium, and a conformal carbonate coating formed at the interface, all highlight new research directions. Although there are still many obstacles to be overcome, we are optimistic that Li metal can be used as an anode in rechargeable batteries in the foreseeable future. This will enable wide

  6. Method for providing adhesion to a metal surface

    DOEpatents

    Harrah, L.A.; Allred, R.E.; Wilson, K.V. Jr.

    1992-02-18

    A process for treating metal surfaces to obtain improved susceptibility to bonding with adhesive compositions is disclosed. A metal surface is oxidized with a halogen to form a monolayer of halide ions on the surface. The halide ions are then exchanged with azide ions to form an azide monolayer on the metal surface. Upon contact of the treated surface with an adhesive composition, the azide layer may be thermally or photochemically decomposed to form active nitrene species, which react to bond the adhesive composition to the metal surface.

  7. Method for providing adhesion to a metal surface

    DOEpatents

    Harrah, Larry A.; Allred, Ronald E.; Wilson, Jr., Kennard V.

    1992-01-01

    A process for treating metal surfaces to obtain improved susceptibility to bonding with adhesive compositions is disclosed. A metal surface is oxidized with a halogen to form a monolayer of halide ions on the surface. The halide ions are then exchanged with azide ions to form an azide monolayer on the metal surface. Upon contact of the treated surface with an adhesive composition, the azide layer may be thermally or photochemically decomposed to form active nitrene species, which react to bond the adhesive composition to the metal surface.

  8. Stability investigation of laser darkened metal surfaces

    NASA Astrophysics Data System (ADS)

    Hopp, Béla; Smausz, Tomi; Lentner, Márton; Kopniczky, Judit; Tápai, Csaba; Gera, Tamás; Csizmadia, Tamás; Ehrhardt, Martin; Lorenz, Pierre; Zimmer, Klaus

    2017-09-01

    Pulsed laser irradiation-induced reflectivity decrease of metal surfaces is a well-established phenomenon, which is extensively utilized in numerous applications. Since the stability of these black surfaces is often a demand, we investigated the resistance of darkened copper and titanium surfaces against optical and mechanical damages. For optical stability studies, samples were irradiated by a probe laser beam ( λ = 775 nm, FWHM = 150 fs, f = 1 kHz) at different fluences (0-300 mJ/cm2), while the mechanical stability was studied with scratch test using 2.5 µm radius tip and applying normal force in 29.4-147 µN range. The observed reflectivity and morphological changes indicated that the optical damage threshold fluence is 130 and 160 mJ/cm2 for copper and titanium surfaces, respectively. Mechanical damage only in case of copper could be detected in the applied parameter range indicating a scratch hardness of 21.5 MPa.

  9. Stereochemical Recognition of Helicenes on Metal Surfaces.

    PubMed

    Ernst, Karl-Heinz

    2016-06-21

    The chiral recognition among biomolecules is fundamentally important for many processes of life, including the stereochemistry of evolution. Of special interest is chiral recognition during crystallization of racemates, when either homochiral recognition leads to a conglomerate of homochiral crystals or heterochiral recognition dominates resulting in a racemic compound. The complex nature of molecular recognition at the level of nucleation and crystal growth renders it difficult to understand and calls for manageable model systems. Notably, the approach of studying aggregation of molecules at surfaces under well-defined conditions includes the benefit of the availability of a multitude of highly sensitive investigation methods, of which scanning tunneling microscopy (STM) with its submolecular resolution is tremendously valuable. Heterogeneous nucleation at surfaces is strongly favored over homogeneous nucleation in solution; hence, surfaces are significantly involved in stereochemical recognition during crystallization. Helicenes are a fascinating class of chiral compounds with outstanding optical activity. These π-conjugated, ortho-fused, aromatic hydrocarbons are promising candidates for organic electronic devices such as sensors, circular dichroic photonics, liquid crystal displays or spin filters. But in particular the defined footprint of their terminal benzo rings on a surface makes them interesting for studying stereochemical recognition with different single crystalline surfaces and the impact this has, in turn, on intermolecular recognition. In this Account, we describe the self-assembly of helicenes on metal surfaces with the focus on stereochemical recognition in two-dimensional structures. Using the isomeric all-carbon helicenes, heptahelicene and dibenzohelicene as examples, different aggregation phenomena on different surfaces of single crystalline copper, silver, and gold are investigated. By means of STM different modes of transmission of

  10. The Surface Structure of Ground Metal Crystals

    NASA Technical Reports Server (NTRS)

    Boas, W.; Schmid, E.

    1944-01-01

    The changes produced on metallic surfaces as a result of grinding and polishing are not as yet fully understood. Undoubtedly there is some more or less marked change in the crystal structure, at least, in the top layer. Hereby a diffusion of separated crystal particles may be involved, or, on plastic material, the formation of a layer in greatly deformed state, with possible recrystallization in certain conditions. Czochralski verified the existence of such a layer on tin micro-sections by successive observations of the texture after repeated etching; while Thomassen established, roentgenographically by means of the Debye-Scherrer method, the existence of diffused crystal fractions on the surface of ground and polished tin bars, which he had already observed after turning (on the lathe). (Thickness of this layer - 0.07 mm). Whether this layer borders direct on the undamaged base material or whether deformed intermediate layers form the transition, nothing is known. One observation ty Sachs and Shoji simply states that after the turning of an alpha-brass crystal the disturbance starting from the surface, penetrates fairly deep (approx. 1 mm) into the crystal (proof by recrystallization at 750 C).

  11. Metallic copper as an antimicrobial surface.

    PubMed

    Grass, Gregor; Rensing, Christopher; Solioz, Marc

    2011-03-01

    Bacteria, yeasts, and viruses are rapidly killed on metallic copper surfaces, and the term "contact killing" has been coined for this process. While the phenomenon was already known in ancient times, it is currently receiving renewed attention. This is due to the potential use of copper as an antibacterial material in health care settings. Contact killing was observed to take place at a rate of at least 7 to 8 logs per hour, and no live microorganisms were generally recovered from copper surfaces after prolonged incubation. The antimicrobial activity of copper and copper alloys is now well established, and copper has recently been registered at the U.S. Environmental Protection Agency as the first solid antimicrobial material. In several clinical studies, copper has been evaluated for use on touch surfaces, such as door handles, bathroom fixtures, or bed rails, in attempts to curb nosocomial infections. In connection to these new applications of copper, it is important to understand the mechanism of contact killing since it may bear on central issues, such as the possibility of the emergence and spread of resistant organisms, cleaning procedures, and questions of material and object engineering. Recent work has shed light on mechanistic aspects of contact killing. These findings will be reviewed here and juxtaposed with the toxicity mechanisms of ionic copper. The merit of copper as a hygienic material in hospitals and related settings will also be discussed.

  12. Towards design rules for covalent nanostructures on metal surfaces.

    PubMed

    Björk, Jonas; Hanke, Felix

    2014-01-20

    The covalent molecular assembly on metal surfaces is explored, outlining the different types of applicable reactions. Density functional calculations for on-surface reactions are shown to yield valuable insights into specific reaction mechanisms and trends across the periodic table. Finally, it is shown how design rules could be derived for nanostructures on metal surfaces.

  13. Method for cleaning and passivating a metal surface

    NASA Technical Reports Server (NTRS)

    Alexander, George B. (Inventor); Carpenter, Norman F. (Inventor)

    1976-01-01

    A cleaning solvent useful in the cleaning of metal surfaces, e.g. nickle-iron alloys, contains sulfamic acid, citric acid, a solvent for hydrocarbon residues, and a surfactant. Metal surfaces are cleaned by contacting the surface with the cleaning solvent and then passivated by contact with aqueous solutions of citric acid or sodium nitrite or a combination of the two.

  14. Vibrations of alkali metal overlayers on metal surfaces

    NASA Astrophysics Data System (ADS)

    Rusina, G. G.; Eremeev, S. V.; Echenique, P. M.; Benedek, G.; Borisova, S. D.; Chulkov, E. V.

    2008-06-01

    We review the current progress in the understanding of vibrations of alkalis adsorbed on metal surfaces. The analysis of alkali vibrations was made on the basis of available theoretical and experimental results. We also include in this discussion our recent calculations of vibrations in K/Pt(111) and Li(Na)/Cu(001) systems. The dependence of alkali adlayer localized modes on atomic mass, adsorption position and coverage as well as the dependence of vertical vibration frequency on the substrate orientation is discussed. The square root of atomic mass dependence of the vertical vibration energy has been confirmed by using computational data for alkalis on the Al(111) and Cu(001) substrates. We have confirmed that in a wide range of submonolayer coverages the stretch mode energy remains nearly constant while the energy of in-plane polarized modes increases with the increase of alkali coverage. It was shown that the spectrum of both stretch and in-plane vibrations can be very sensitive to the adsorption position of alkali atoms and substrate orientation.

  15. Orbitalwise Coordination Number for Predicting Adsorption Properties of Metal Nanocatalysts.

    PubMed

    Ma, Xianfeng; Xin, Hongliang

    2017-01-20

    We present the orbitalwise coordination number CN^{α} (α=s or d) as a reactivity descriptor for metal nanocatalysts. With the noble metal Au (5d^{10}6s^{1}) as a specific case, the CN^{s} computed using the two-center s-electron hopping integrals to neighboring atoms provides an accurate and robust description of the trends in CO and O adsorption energies on extended surfaces terminated with different facets and nanoparticles of varying size and shape, outperforming existing bond-counting methods. Importantly, the CN^{s} has a solid physiochemical basis via a direct connection to the moment characteristics of the projected density of states onto the s orbital of a Au adsorption site. Furthermore, the CN^{s} shows promise as a viable descriptor for predicting adsorption properties of Au alloy nanoparticles with size-dependent lattice strains and coinage metal ligands.

  16. Orbitalwise Coordination Number for Predicting Adsorption Properties of Metal Nanocatalysts

    NASA Astrophysics Data System (ADS)

    Ma, Xianfeng; Xin, Hongliang

    2017-01-01

    We present the orbitalwise coordination number CNα (α =s or d ) as a reactivity descriptor for metal nanocatalysts. With the noble metal Au (5 d106 s1 ) as a specific case, the CNs computed using the two-center s -electron hopping integrals to neighboring atoms provides an accurate and robust description of the trends in CO and O adsorption energies on extended surfaces terminated with different facets and nanoparticles of varying size and shape, outperforming existing bond-counting methods. Importantly, the CNs has a solid physiochemical basis via a direct connection to the moment characteristics of the projected density of states onto the s orbital of a Au adsorption site. Furthermore, the CNs shows promise as a viable descriptor for predicting adsorption properties of Au alloy nanoparticles with size-dependent lattice strains and coinage metal ligands.

  17. Method for preparing hydride configurations and reactive metal surfaces

    DOEpatents

    Silver, Gary L.

    1988-08-16

    A method for preparing highly hydrogen-reactive surfaces on metals which normally require substantial heating, high pressures, or an extended induction period, which involves pretreatment of said surfaces with either a non-oxidizing acid or hydrogen gas to form a hydrogen-bearing coating on said surfaces, and subsequently heating said coated metal in the absence of moisture and oxygen for a period sufficient to decompose said coating and cooling said metal to room temperature. Surfaces so treated will react almost instantaneously with hydrogen gas at room temperature and low pressure. The method is particularly applicable to uranium, thorium, and lanthanide metals.

  18. Eigen kinetics in surface complexation of aqueous metal ions.

    PubMed

    van Leeuwen, Herman P

    2008-10-21

    The mechanism of chemisorption of aqueous metal ions at surfaces has long been a topical issue in such fields as soil chemistry and bioenvironmental science. Here it is quantitatively demonstrated for the first time that release of water from the inner hydration shell is the rate-limiting step in inner-sphere surface complexation. The reactive intermediate is an outer-sphere complex between metal ion and surface site, with an electrostatically controlled stability defined by Boltzmann statistics. Using tabulated dehydration rate constants for metal ions, the resulting scheme allows for prediction of rates of sorption of aqueous metal ions at any type of complexing surface.

  19. Composition and Method for Cleaning Salt Residues From Metal Surfaces.

    DTIC Science & Technology

    CLEANING, *METALS), (*AIRCRAFT ENGINES, CLEANING), (*PATENTS, CLEANING), ETHYLENEDINITRILO TETRAACETATES, SALTS , HELICOPTER ENGINES...ETHYLENEDIAMINE, SODIUM COMPOUNDS, POLYETHYLENE PLASTICS, PROPENES, SURFACE ACTIVE SUBSTANCES, ACETATES, CORROSION, NITRITES

  20. Sink property of metallic glass free surfaces

    SciTech Connect

    Shao, Lin; Fu, Engang; Price, Lloyd; Chen, Di; Chen, Tianyi; Wang, Yongqiang; Xie, Guoqiang; Lucca, Don A.

    2015-03-16

    When heated to a temperature close to glass transition temperature, metallic glasses (MGs) begin to crystallize. Under deformation or particle irradiation, crystallization occurs at even lower temperatures. Hence, phase instability represents an application limit for MGs. Here, we report that MG membranes of a few nanometers thickness exhibit properties different from their bulk MG counterparts. The study uses in situ transmission electron microscopy with concurrent heavy ion irradiation and annealing to observe crystallization behaviors of MGs. For relatively thick membranes, ion irradiations introduce excessive free volumes and thus induce nanocrystal formation at a temperature linearly decreasing with increasing ion fluences. For ultra-thin membranes, however, the critical temperature to initiate crystallization is about 100 K higher than the bulk glass transition temperature. Molecular dynamics simulations indicate that this effect is due to the sink property of the surfaces which can effectively remove excessive free volumes. These findings suggest that nanostructured MGs having a higher surface to volume ratio are expected to have higher crystallization resistance, which could pave new paths for materials applications in harsh environments requiring higher stabilities.

  1. Sink property of metallic glass free surfaces

    DOE PAGES

    Shao, Lin; Fu, Engang; Price, Lloyd; ...

    2015-03-16

    When heated to a temperature close to glass transition temperature, metallic glasses (MGs) begin to crystallize. Under deformation or particle irradiation, crystallization occurs at even lower temperatures. Hence, phase instability represents an application limit for MGs. Here, we report that MG membranes of a few nanometers thickness exhibit properties different from their bulk MG counterparts. The study uses in situ transmission electron microscopy with concurrent heavy ion irradiation and annealing to observe crystallization behaviors of MGs. For relatively thick membranes, ion irradiations introduce excessive free volumes and thus induce nanocrystal formation at a temperature linearly decreasing with increasing ion fluences.more » For ultra-thin membranes, however, the critical temperature to initiate crystallization is about 100 K higher than the bulk glass transition temperature. Molecular dynamics simulations indicate that this effect is due to the sink property of the surfaces which can effectively remove excessive free volumes. These findings suggest that nanostructured MGs having a higher surface to volume ratio are expected to have higher crystallization resistance, which could pave new paths for materials applications in harsh environments requiring higher stabilities.« less

  2. Surface wave holography on designing subwavelength metallic structures.

    PubMed

    Chen, Yu-Hui; Fu, Jin-Xin; Li, Zhi-Yuan

    2011-11-21

    We report a method in the framework of surface wave holography to manipulate the electromagnetic wave on the metallic surface for realizing complicated electromagnetic wave transport functionalities in three-dimensional (3D) space. The method allows for direct determination of the metallic surface structure morphology for a given transport functionality, by means of writing desirable object information on the metallic surface via interference with a reference surface wave. We have employed the analytical approach to design and build metallic surface structures that realize arbitrary single-point focusing, arbitrary single-direction beam collimation, and simultaneous two-point focusing of electromagnetic wave in 3D space. Good agreement between numerical simulations and microwave experimental measurements has been found and confirms the power of the method in conceptually understanding and exploiting the surface electromagnetic wave on subwavelength metal structures.

  3. X-ray Fluorescence analytical criteria to assess the fineness of ancient silver coins: Application on Ptolemaic coinage

    NASA Astrophysics Data System (ADS)

    Kantarelou, Vasiliki; Ager, Francisco José; Eugenidou, Despoina; Chaves, Francisca; Andreou, Alexandros; Kontou, Elena; Katsikosta, Niki; Respaldiza, Miguel Angel; Serafin, Patrizia; Sokaras, Dimosthenis; Zarkadas, Charalambos; Polikreti, Kyriaki; Karydas, Andreas Germanos

    2011-09-01

    The application of X-ray Fluorescence (XRF) analysis in a non-invasive manner on ancient silver coins may not provide reliable bulk compositional data due to possible presence of a surface, silver enriched layer. The present work proposes a set of three complementary analytical methodologies to assess and improve the reliability of XRF data in such cases: a) comparison of XRF data on original and cleaned micro-spots on coin surface, b) Ag K/L ratio test and c) comparison of experimental and theoretically simulated intensities of the Rayleigh characteristic radiation emitted from the anode. The proposed methodology was applied on 82 silver coins from the collection of Ioannes Demetriou, donated to the Numismatic Museum of Athens in the 1890s. The coins originate from different mints and are attributed to the first five Ptolemaic kings' reign (321-180 B.C.). They were analyzed in-situ by using a milli-probe XRF spectrometer. The presence of an Ag-enriched layer was excluded for the majority of them. The silver fineness was found to be high, with very low concentrations of copper and lead. The composition data provide important information about possible sources of silver during the Ptolemaic period and indications of a gradual coinage debasement after 270 B.C. due to economic or technical reasons.

  4. Photoelectric scanner makes detailed work function maps of metal surface

    NASA Technical Reports Server (NTRS)

    Rasor, N. S.

    1966-01-01

    Photoelectric scanning device maps the work function of a metal surface by scanning it with a light spot and measuring the resulting photocurrent. The device is capable of use over a range of surface temperatures.

  5. Dependence of metal-enhanced fluorescence on surface roughness

    NASA Astrophysics Data System (ADS)

    François, Alexandre; Sciacca, Beniamino; Zuber, Agnieszka; Klantsataya, Elizaveta; Monro, Tanya M.

    2014-03-01

    Metal Enhanced Fluorescence (MEF) takes advantage of the coupling between surface plasmons, in either a metallic thin film or metallic nanoparticles, and fluorophores located in proximity of the metal, yielding an increase of the fluorophore emission. While MEF has been widely studied on metallic nanoparticles with the emphasis on creating brighter fluorescent labels, planar surfaces have not benefitted from the same attention. Here we investigate the influence of the surface roughness of a thin metallic film on the fluorescence enhancement. 50nm thick silver films were deposited on glass slides using either thermal evaporation with different evaporation currents or an electroless plating method based on the Tollens reaction to vary the surface roughness. Multiple layers of positively and negatively charged polyelectrolytes were deposited on top of the metallic coating to map out the enhancement factor as function of the gap between the metallic coating and fluorophore molecules covalently bound to the last polyelectrolyte layer. We show that fluorescence is enhanced by the presence of the metallic film, and in particular that the enhancement increases by a factor 3 to 40 for roughness ranging from 3 nm to 8 nm. Although these enhancement factors are modest compared to the enhancement produced by complex metallic nanoparticles or nano-patterned metallic thin films, the thin films used here are capable of supporting a plasmonic wave and offer the possibility of combining different techniques, such as surface plasmon resonance (with its higher refractive index sensitivity compared to localized plasmons) and MEF within a single device.

  6. Process to restore obliterated serial numbers on metal surfaces

    NASA Technical Reports Server (NTRS)

    Young, S. G.; Parker, B.; Chisum, W. J.

    1974-01-01

    Metal smeared into grooves of serial numbers by grinding or filing can be cleaned out by process called cavitation. Ultrasonic vibrator generates very high frequency vibrations in water which create millions of microscopic bubbles. Cavitation bubbles impact metal surface at thousands of pounds per square inch pressure. Metal particles filling grooves are broken away.

  7. Surface enhanced Raman scattering with metal nanoshells

    NASA Astrophysics Data System (ADS)

    Jackson, Joseph Bryan

    A systematic investigation of surface enhanced Raman scattering (SERS) was performed using metal nanoshells as the substrate. Nanoshells are a dielectric sphere coated with a thin metal shell, which have a well understood, geometrically tunable plasmon resonance. This tunability allows for the engineering of the optical near field for SERS. A simple model connecting the nanoshell electromagnetic near field at the incident frequency to that at the Raman shifted frequency is discussed. This theory is compared to the measured SERS response of the nonresonant molecule para-mercaptoaniline (pMA) adsorbed on silver and gold nanoshells. Using a solution of silver nanoshells, at an excitation wavelength of 1064 nm enhancements on the order of 106 to 108 were observed. Accounting for reabsorption of the Raman scattered light as it traverses the solution suggests enhancements of 1012. To mitigate the reabsorption, film geometries were investigated. For film measurements a 782 nm excitation laser was used. The SERS response of a dense film of silver nanoshells followed the calculated single nanoshell response of the nanoshells whose plasmon resonance was tuned near the excitation wavelength. In contrast, for nanoshells blue shifted from the excitation laser, the film Raman response followed an estimated dimer response. The Raman response as a function of nanoshell density was studied using films of gold nanoshells dispersed on the surface of polyvinylpyridine (PVP) coated glass slides. A linear dependence of the Raman modes on the nanoshell density was observed confirming that the single nanoshell plasmon dominates the SERS response. The SERS enhancements for nanoshell films calculated by direct comparison to an unenhanced measurement were on the order of 10 10 to 1012. The Raman response as a function of incident intensity was measured for dense silver nanoshell films. An optical pumping model allowing for stimulation of the Raman emission is proposed. Using this model, an

  8. Heat transfer performance of metal fiber sintered surfaces

    NASA Astrophysics Data System (ADS)

    Kajikawa, T.; Takazawa, H.; Mizuki, M.

    1983-03-01

    Boiling heat transfer performance on stainless steel metal fiber sintered surfaces is experimentally investigated with Freon 11 (R11) as the working fluid. The boiling heat transfer coefficient for the optimum surface structure gives a tenfold improvement over a smooth surface. The nondimensional specific parameter including all design parameters is introduced to explain the trend of the performance of various kinds of metal fiber sintered surfaces. Moreover, the metal fiber sintered surface clad with titanium film is suggested to be appropriate to an evaporator for Ocean Thermal Energy Conversion (OTEC) system.

  9. Surface treatment and modification of metals to add biofunction.

    PubMed

    Hanawa, Takao

    2017-09-26

    To add biocompatibility or biofunction to metal surface, an intelligent interface between metals and tissues must be acquired. Tremendous surface modification techniques are currently studied to create the intelligent interface. In particular, bone formation or bone bonding is major purpose of the surface modifications. Time transient of surface modification techniques are summarized and the importance of roughened or porous surface to combine materials with bone tissue is demonstrated. As an example of surface modification, electrodeposition of poly(ethylene glycol) to inhibit biofilm formation is introduced. A dual-functional surface is formed on titanium by micro arc oxidation. In addition, the effect of topography on the elongation and differentiation of human mesenchymal stem cells was confirmed on the hybrid micrometer-level and nanometer-level grooves of titanium surface. Metal surface is possibly biofunctionalized by various surface modification techniques.

  10. Non-destructive photoacoustic imaging of metal surface defects

    NASA Astrophysics Data System (ADS)

    Jeon, Seungwan; Kim, Jeesu; Yun, Jong Pil; Kim, Chulhong

    2016-11-01

    The detection of metal surface defects is important in achieving the goals of product quality enhancement and manufacturing cost reduction. Identifying the defects with visual inspection is difficult, inaccurate, and time-consuming. Thus, several inspection methods using line cameras, magnetic field, and ultrasound have been proposed. However, identifying small defects on metal surfaces remains a challenge. To deal with this problem, we propose the use of photoacoustic imaging (PAI) as a new non-destructive imaging tool to detect metal surface defects. We successfully visualized two types of cracks (i.e., unclassified and seam cracks) in metal plate samples using PAI. In addition, we successfully extracted cracked edges from height-encoded photoacoustic maximum amplitude projection images using the Laplacian of Gaussian filtering method, and then, quantified the detected edges for a statistical analysis. We concluded that PAI can be useful in detecting metal surface defects reducing the defect rate and manufacturing cost during metal production.

  11. Electrostatic potentials for metal-oxide surfaces and interfaces

    NASA Astrophysics Data System (ADS)

    Streitz, F. H.; Mintmire, J. W.

    1994-10-01

    As most technologically important metals will form oxides readily, any complete study of adhesion at real metal surfaces must include the metal-oxide interface. The role of this ubiquitous oxide layer cannot be overlooked, as the adhesive properties of the oxide or oxide-metal system can be expected to differ profoundly from the adhesive properties of a bare metal surface. We report on the development of a computational method for molecular-dynamics simulations, which explicitly includes variable charge transfer between anions and cations. This method is found to be capable of describing the elastic properties, surface energies, and surface relaxation of crystalline metal oxides accurately. We discuss in detail results using this method for α-alumina and several of its low-index faces.

  12. Dynamic interactions of Leidenfrost droplets on liquid metal surface

    NASA Astrophysics Data System (ADS)

    Ding, Yujie; Liu, Jing

    2016-09-01

    Leidenfrost dynamic interaction effects of the isopentane droplets on the surface of heated liquid metal were disclosed. Unlike conventional rigid metal, such conductive and deformable liquid metal surface enables the levitating droplets to demonstrate rather abundant and complex dynamics. The Leidenfrost droplets at different diameters present diverse morphologies and behaviors like rotation and oscillation. Depending on the distance between the evaporating droplets, they attract and repulse each other through the curved surfaces beneath them and their vapor flows. With high boiling point up to 2000 °C, liquid metal offers a unique platform for testing the evaporating properties of a wide variety of liquid even solid.

  13. Engineering Polarons at a Metal Oxide Surface

    NASA Astrophysics Data System (ADS)

    Yim, C. M.; Watkins, M. B.; Wolf, M. J.; Pang, C. L.; Hermansson, K.; Thornton, G.

    2016-09-01

    Polarons in metal oxides are important in processes such as catalysis, high temperature superconductivity, and dielectric breakdown in nanoscale electronics. Here, we study the behavior of electron small polarons associated with oxygen vacancies at rutile TiO2(110 ) , using a combination of low temperature scanning tunneling microscopy (STM), density functional theory, and classical molecular dynamics calculations. We find that the electrons are symmetrically distributed around isolated vacancies at 78 K, but as the temperature is reduced, their distributions become increasingly asymmetric, confirming their polaronic nature. By manipulating isolated vacancies with the STM tip, we show that particular configurations of polarons are preferred for given locations of the vacancies, which we ascribe to small residual electric fields in the surface. We also form a series of vacancy complexes and manipulate the Ti ions surrounding them, both of which change the associated electronic distributions. Thus, we demonstrate that the configurations of polarons can be engineered, paving the way for the construction of conductive pathways relevant to resistive switching devices.

  14. Surface plasmon interference spectroscopy of metal films

    NASA Astrophysics Data System (ADS)

    Vlasko-Vlasov, Vitalii; Welp, Ulrich; Rydh, Andreas; Pearson, John

    2006-03-01

    Circular nanoslits manufactured by focused ion beam in silver films were used to excite surface plasmon polaritons and to generate plasmon interference patterns. Changes of the plasmon interference periods at changing the excitation wavelength were imaged by a near-field scanning optical microscope and scaled by the known nanostructure dimensions allowing precise plasmon wavelength measurements. The plasmon dispersion curves for our film thickness were calculated in different approximations and a proper fitting function for the experimental data was chosen. This allowed to retrieve the frequency dependence of the dielectric function of our silver film, which is different from usually cited Johnson-Christy and Palik data but falls in the range of values reported in literature. The results of fitting indicate to the important role of losses, which can not be neglected in definition of the real part of the dielectric constant even in the Drude region. Our technique is a useful tool for the local characterization of the dielectric function sensitive to the structure of metal films potential for photonics applications.

  15. Pendant-Drop Surface-Tension Measurement On Molten Metal

    NASA Technical Reports Server (NTRS)

    Man, Kin Fung; Thiessen, David

    1996-01-01

    Method of measuring surface tension of molten metal based on pendant-drop method implemented in quasi-containerless manner and augmented with digital processing of image data. Electrons bombard lower end of sample rod in vacuum, generating hanging drop of molten metal. Surface tension of drop computed from its shape. Technique minimizes effects of contamination.

  16. Metal-dielectric hybrid surfaces as integrated optoelectronic interfaces

    DOEpatents

    Narasimhan, Vijay K.; Hymel, Thomas M.; Lai, Ruby A.; Cui, Yi

    2017-01-03

    An optoelectronic device has a hybrid metal-dielectric optoelectronic interface including an array of nanoscale dielectric resonant elements (e.g., nanopillars), and a metal film disposed between the dielectric resonant elements and below a top surface of the resonant elements such that the dielectric resonant elements protrude through the metal film. The device may also include an anti-reflection coating. The device may further include a metal film layer on each of the dielectric resonant elements.

  17. 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.

  18. 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.

  19. Recent applications of liquid metals featuring nanoscale surface oxides

    NASA Astrophysics Data System (ADS)

    Neumann, Taylor V.; Dickey, Michael D.

    2016-05-01

    This proceeding describes recent efforts from our group to control the shape and actuation of liquid metal. The liquid metal is an alloy of gallium and indium which is non-toxic, has negligible vapor pressure, and develops a thin, passivating surface oxide layer. The surface oxide allows the liquid metal to be patterned and shaped into structures that do not minimize interfacial energy. The surface oxide can be selectively removed by changes in pH or by applying a voltage. The surface oxide allows the liquid metal to be 3D printed to form free-standing structures. It also allows for the liquid metal to be injected into microfluidic channels and to maintain its shape within the channels. The selective removal of the oxide results in drastic changes in surface tension that can be used to control the flow behavior of the liquid metal. The metal can also wet thin, solid films of metal that accelerates droplets of the liquid along the metal traces .Here we discuss the properties and applications of liquid metal to make soft, reconfigurable electronics.

  20. Landau damping of surface plasmons in metal nanostructures

    NASA Astrophysics Data System (ADS)

    Shahbazyan, Tigran V.

    2016-12-01

    We develop a quantum-mechanical theory for Landau damping of surface plasmons in metal nanostructures of arbitrary shape. We show that the electron surface scattering, which facilitates plasmon decay in small nanostructures, can be incorporated into the metal dielectric function on par with phonon and impurity scattering. The derived surface scattering rate is determined by the local field polarization relative to the metal-dielectric interface and is highly sensitive to the system geometry. We illustrate our model by providing analytical results for surface scattering rate in some common shape nanostructures. Our results can be used for calculations of hot carrier generation rates in photovoltaics and photochemistry applications.

  1. Image current heating on metal surface due to charged bunches

    SciTech Connect

    Lin, X.

    2000-02-28

    When charged particles pass through a metal pipe, they are accompanied by an image current on the metal surface. With intense short bunches passing near the metal surface, the peak image current density can be very high. This current may result in substantial temperature rise on the surface, especially in multi-bunch operation. In this paper, the authors derive an explicit formula for the surface temperature rise due to this previously unrecognized effect, and show that it should be taken into account in structure and collimator design for future accelerators.

  2. The Incorporation of Added Metal Atoms into Structures of Reaction Intermediates on Catalytic Metal Surfaces

    NASA Astrophysics Data System (ADS)

    Zhou, Ling; Madix, Robert J.

    In this chapter, we review the dynamic nature of catalytic metal surfaces and the effects of metal incorporation into surface reaction intermediates on their reactivity. Scanning tunneling microscopy allows the direct observation of surface reconstruction and dynamic reorganization of surfaces during adsorption, desorption, and surface reaction, and therefore, provides a powerful tool to relate the surface structures of adsorbed layers to reactivity when combined with quantitative temperature-programmed reaction spectroscopy, X-ray photoelectron spectroscopy and other tools. The incorporation of added metal atoms to the structure of adsorbates and reaction intermediates is a general surface phenomenon not restricted to more open, higher free energy single crystal planes, but also occurring on close-packed surfaces of low free energy. Metal atom incorporation into the surface oxide appears to be a guide to the possibility of incorporation of metal atoms into the structure of other intermediates. Added metal atoms can stabilize the structures of reaction intermediates and play an important role in their surface reactions. These observations dictate that the participation of added metal atoms be considered as a paradigm in metal catalyzed reactions, significantly affecting the theoretical treatment of these processes.

  3. He atom surface spectroscopy: Surface lattice dynamics of insulators, metals and metal overlayers

    SciTech Connect

    Not Available

    1990-01-01

    During the first three years of this grant (1985--1988) the effort was devoted to the construction of a state-of-the-art He atom scattering (HAS) instrument which would be capable of determining the structure and dynamics of metallic, semiconductor or insulator crystal surfaces. The second three year grant period (1988--1991) has been dedicated to measurements. The construction of the instrument went better than proposed; it was within budget, finished in the proposed time and of better sensitivity and resolution than originally planned. The same success has been carried over to the measurement phase where the concentration has been on studies of insulator surfaces, as discussed in this paper. The experiments of the past three years have focused primarily on the alkali halides with a more recent shift to metal oxide crystal surfaces. Both elastic and inelastic scattering experiments were carried out on LiF, NaI, NaCl, RbCl, KBr, RbBr, RbI, CsF, CsI and with some preliminary work on NiO and MgO.

  4. 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.

  5. Cell surface engineering of microorganisms towards adsorption of heavy metals.

    PubMed

    Li, Peng-Song; Tao, Hu-Chun

    2015-06-01

    Heavy metal contamination has become a worldwide environmental concern due to its toxicity, non-degradability and food-chain bioaccumulation. Conventional physical and chemical treatment methods for heavy metal removal have disadvantages such as cost-intensiveness, incomplete removal, secondary pollution and the lack of metal specificity. Microbial biomass-based biosorption is one of the approaches gaining increasing attention because it is effective, cheap, and environmental friendly and can work well at low concentrations. To enhance the adsorption properties of microbial cells to heavy metal ions, the cell surface display of various metal-binding proteins/peptides have been performed using a cell surface engineering approach. The surface engineering of Gram-negative bacteria, Gram-positive bacteria and yeast towards the adsorption of heavy metals are reviewed in this article. The problems and future perspectives of this technology are discussed.

  6. Metal ion-exchange on the muscovite mica surface

    NASA Astrophysics Data System (ADS)

    de Poel, Wester; Vaessen, Sarah L.; Drnec, Jakub; Engwerda, Anthonius H. J.; Townsend, Eleanor R.; Pintea, Stelian; de Jong, Aryan E. F.; Jankowski, Maciej; Carlà, Francesco; Felici, Roberto; Elemans, Johannes A. A. W.; van Enckevort, Willem J. P.; Rowan, Alan E.; Vlieg, Elias

    2017-11-01

    The surface potassium ions of muscovite mica were exchanged for several different metal ions from aqueous solution (Ag, Ca, V, Mn, Fe, Ni, Cu, Zn, Co, and Cd). The surfaces were rinsed in water, dried under nitrogen atmosphere, and subsequently analysed using atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and, for half the systems, surface X-ray diffraction (SXRD). XPS and SXRD confirmed the presence of the different metal ions at the muscovite mica surface, with a partial monolayer of the monovalent and divalent ions present on the surface. No counter ions from the used salts were detected. AFM revealed that Ni-, and Fe-terminated muscovite mica surfaces were partially covered by nanoparticles, most likely consisting of metal (hydr)oxide. The exchanged ions remained on the surface after rinsing with ultra pure water three times. SXRD showed that Cd and Ag have a lower affinity for the muscovite mica surface than Cu, Ca, and Mn.

  7. 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.

  8. Metal-organic framework materials with ultrahigh surface areas

    DOEpatents

    Farha, Omar K.; Hupp, Joseph T.; Wilmer, Christopher E.; Eryazici, Ibrahim; Snurr, Randall Q.; Gomez-Gualdron, Diego A.; Borah, Bhaskarjyoti

    2015-12-22

    A metal organic framework (MOF) material including a Brunauer-Emmett-Teller (BET) surface area greater than 7,010 m.sup.2/g. Also a metal organic framework (MOF) material including hexa-carboxylated linkers including alkyne bond. Also a metal organic framework (MOF) material including three types of cuboctahedron cages fused to provide continuous channels. Also a method of making a metal organic framework (MOF) material including saponifying hexaester precursors having alkyne bonds to form a plurality of hexa-carboxylated linkers including alkyne bonds and performing a solvothermal reaction with the plurality of hexa-carboxylated linkers and one or more metal containing compounds to form the MOF material.

  9. Staphylococcal Surface Display of Metal-Binding Polyhistidyl Peptides

    PubMed Central

    Samuelson, Patrik; Wernérus, Henrik; Svedberg, Malin; Ståhl, Stefan

    2000-01-01

    Recombinant Staphylococcus xylosus and Staphylococcus carnosus strains were generated with surface-exposed chimeric proteins containing polyhistidyl peptides designed for binding to divalent metal ions. Surface accessibility of the chimeric surface proteins was demonstrated and the chimeric surface proteins were found to be functional in terms of metal binding, since the recombinant staphylococcal cells were shown to have gained Ni2+- and Cd2+-binding capacity, suggesting that such bacteria could find use in bioremediation of heavy metals. This is, to our knowledge, the first time that recombinant, surface-exposed metal-binding peptides have been expressed on gram-positive bacteria. Potential environmental or biosensor applications for such recombinant staphylococci as biosorbents are discussed. PMID:10698802

  10. Visualization of latent fingerprint corrosion of metallic surfaces.

    PubMed

    Bond, John W

    2008-07-01

    Chemical reactions between latent fingerprints and a variety of metal surfaces are investigated by heating the metal up to temperatures of approximately 600 degrees C after deposition of the fingerprint. Ionic salts present in the fingerprint residue corrode the metal surface to produce an image of the fingerprint that is both durable and resistant to cleaning of the metal. The degree of fingerprint enhancement appears independent of the elapsed time between deposition and heating but is very dependent on both the composition of the metal and the level of salt secretion by the fingerprint donor. Results are presented that show practical applications for the enhancement to fingerprints deposited in arson crime scenes, contaminated by spray painting, or deposited on brass cartridge cases prior to discharge. The corrosion of the metal surface is further exploited by the demonstration of a novel technique for fingerprint enhancement based on the electrostatic charging of the metal and then the preferential adherence of a metallic powder to the corroded part of the metal surface.

  11. Antimicrobial metallic copper surfaces kill Staphylococcus haemolyticus via membrane damage

    PubMed Central

    Santo, Christophe Espírito; Quaranta, Davide; Grass, Gregor

    2012-01-01

    Recently, copper (Cu) in its metallic form has regained interest for its antimicrobial properties. Use of metallic Cu surfaces in worldwide hospital trials resulted in remarkable reductions in surface contaminations. Yet, our understanding of why microbes are killed upon contact to the metal is still limited and different modes of action have been proposed. This knowledge, however, is crucial for sustained use of such surfaces in hospitals and other hygiene-sensitive areas. Here, we report on the molecular mechanisms by which the Gram-positive Staphylococcus haemolyticus is inactivated by metallic Cu. Staphylococcus haemolyticus was killed within minutes on Cu but not on stainless steel demonstrating the antimicrobial efficacy of metallic Cu. Inductively coupled plasma mass spectroscopy (ICP-MS) analysis and in vivo staining with Coppersensor-1 indicated that cells accumulated large amounts of Cu ions from metallic Cu surfaces contributing to lethal damage. Mutation rates of Cu- or steel-exposed cells were similarly low. Instead, live/dead staining indicated cell membrane damage in Cu- but not steel-exposed cells. These findings support a model of the cellular targets of metallic Cu toxicity in bacteria, which suggests that metallic Cu is not genotoxic and does not kill via DNA damage. In contrast, membranes constitute the likely Achilles’ heel of Cu surface-exposed cells. PMID:22950011

  12. A local view of bonding and diffusion at metal surfaces

    SciTech Connect

    Feibelman, P.J.

    1996-09-01

    First-principles density functional calculations and corresponding experimental results underline the importance of basic chemical concepts, such as coordination, valence saturation and promotion-hybridization energetics, in understanding bonding and diffusion of atoms at and on metal surfaces. Several examples are reviewed, including outer-layer relaxations of clean hcp(0001) surfaces, liquid-metal-embrittlement energetics, separation energies of metal-adatom dimers, concerted substitutional self-diffusion on fcc(001) surfaces, and adsorption and diffusion barrier sites for adatoms near steps.

  13. 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.

  14. Thermodynamics of elastic strength of the metal surface layer

    NASA Astrophysics Data System (ADS)

    Andreev, Yu. Ya.; Kiselev, D. A.

    2013-07-01

    This paper presents a physicochemical model that establishes a connection between the elastic strength of the surface layer (SL) of metal and its surface Gibbs energy. The elastic limit of SL along the low-index face of the metal single crystal under stress during the transition from elastic to plastic deformation was calculated. Calculation shows that the elastic limit of metal SL with fcc and bcc structures is approximately three orders of magnitude higher than the yield strength of these metals in bulk and close to nanohardness of the metals, in particular; for Cu(111) и Al(111), it is 5.3 and 2.8 GPa, respectively. In the light of the proposed model, the effect of lowering the elastic strength of metal SL due to adsorption of surfactant is formulated.

  15. Asymmetric light reflectance from metal nanoparticle arrays on dielectric surfaces

    NASA Astrophysics Data System (ADS)

    Huang, K.; Pan, W.; Zhu, J. F.; Li, J. C.; Gao, N.; Liu, C.; Ji, L.; Yu, E. T.; Kang, J. Y.

    2015-12-01

    Asymmetric light reflectance associated with localized surface plasmons excited in metal nanoparticles on a quartz substrate is observed and analyzed. This phenomenon is explained by the superposition of two waves, the wave reflected by the air/quartz interface and that reflected by the metal nanoparticles, and the resulting interference effects. Far field behavior investigation suggests that zero reflection can be achieved by optimizing the density of metal nanoparticles. Near field behavior investigation suggests that the coupling efficiency of localized surface plasmon can be additionally enhanced by separating the metal NPs from substrates using a thin film with refractive index smaller than the substrate. The latter behavior is confirmed via surface-enhanced Raman spectroscopy studies using metal nanoparticles on Si/SiO2 substrates.

  16. Asymmetric light reflectance from metal nanoparticle arrays on dielectric surfaces.

    PubMed

    Huang, K; Pan, W; Zhu, J F; Li, J C; Gao, N; Liu, C; Ji, L; Yu, E T; Kang, J Y

    2015-12-18

    Asymmetric light reflectance associated with localized surface plasmons excited in metal nanoparticles on a quartz substrate is observed and analyzed. This phenomenon is explained by the superposition of two waves, the wave reflected by the air/quartz interface and that reflected by the metal nanoparticles, and the resulting interference effects. Far field behavior investigation suggests that zero reflection can be achieved by optimizing the density of metal nanoparticles. Near field behavior investigation suggests that the coupling efficiency of localized surface plasmon can be additionally enhanced by separating the metal NPs from substrates using a thin film with refractive index smaller than the substrate. The latter behavior is confirmed via surface-enhanced Raman spectroscopy studies using metal nanoparticles on Si/SiO2 substrates.

  17. Structure, Bonding and Surface Chemistry of Metal Oxide Nanoclusters

    DTIC Science & Technology

    2015-06-23

    Rh, as well as those of vanadium oxides. In synthetic experiments, metal oxide clusters are captured from the gas phase into solution, stabilized with... clusters . Additional work has examined vanadium carbide clusters as well as metal-silicon clusters of several transition metals. These ultra-small... clusters are studied with laser desorption and electrospray ionization mass spectrometry, optical spectroscopy methods (IR, surface-enhanced Raman, UV

  18. Molecular Spectroscopy at Corrugated Metal Surfaces

    DTIC Science & Technology

    1988-10-01

    the authors, with emphasis on the effects due to surface corrugations. Examples which illustrate possible applications of such studies in the areas of surface photochemistry and heterogeneous catalysis are also discussed.

  19. Polarity-driven surface metallicity in SmB6

    NASA Astrophysics Data System (ADS)

    Damascelli, Andrea; Zhu, Z.-H.; Nicolaou, A.; Levy, G.; Butch, N. P.; Syers, P.; Wang, X. F.; Paglione, J.; Sawatzky, G. A.; Elfimov, I. S.

    2014-03-01

    By a combined angle-resolved photoemission spectroscopy and density functional theory study, we discover that the surface metallicity is polarity driven in SmB6. Two surface states, not accounted for by the bulk band structure, are reproduced by slab calculations for coexisting B6 and Sm surface terminations. Our analysis reveals that a metallic surface state stems from an unusual property, generic to the (001) termination of all hexaborides: the presence of boron 2 p dangling bonds, on a polar surface. The discovery of polarity-driven surface metallicity sheds new light on the 40-year old conundrum of the low temperature residual conductivity of SmB6, and raises a fundamental question in the field of topological Kondo insulators regarding the interplay between polarity and nontrivial topological properties.

  20. Polarity-Driven Surface Metallicity in SmB6

    NASA Astrophysics Data System (ADS)

    Zhu, Z.-H.; Nicolaou, A.; Levy, G.; Butch, N. P.; Syers, P.; Wang, X. F.; Paglione, J.; Sawatzky, G. A.; Elfimov, I. S.; Damascelli, A.

    2013-11-01

    By a combined angle-resolved photoemission spectroscopy and density functional theory study, we discover that the surface metallicity is polarity driven in SmB6. Two surface states, not accounted for by the bulk band structure, are reproduced by slab calculations for coexisting B6 and Sm surface terminations. Our analysis reveals that a metallic surface state stems from an unusual property, generic to the (001) termination of all hexaborides: the presence of boron 2p dangling bonds, on a polar surface. The discovery of polarity-driven surface metallicity sheds new light on the 40-year old conundrum of the low-temperature residual conductivity of SmB6, and raises a fundamental question in the field of topological Kondo insulators regarding the interplay between polarity and nontrivial topological properties.

  1. Phonons on the clean metal surfaces and in adsorption structures

    NASA Astrophysics Data System (ADS)

    Rusina, Galina G.; Chulkov, Evgenii V.

    2013-06-01

    The state-of-the-art studies of the vibrational dynamics of clean metal surfaces and metal surface structures formed upon the sub-monolayer adsorption of the atoms of various elements are considered. A brief historical survey of the milestones of investigations of surface phonons is presented. The results of studies of the atomic structure and vibration characteristics of surfaces with low and high Miller indices and adsorption structures are analyzed. It is demonstrated that vicinal surfaces of FCC metals tend to exhibit specific vibrational modes located on the step and polarized along the step. Irrespective of the type and position of adsorption or the substrate structure, the phonon spectra of sub-monolayer adsorption structures always tend to display two modes for combined translational displacements of adatoms and for coupled vibrations of substrate atoms and adatoms polarized in the direction normal to the surface. The bibliography includes 202 references.

  2. Preparation of metal surfaces for application of functional coatings

    NASA Astrophysics Data System (ADS)

    Gabdrakhmanov, Az T.; Israphilov, I. H.; Galiakbarov, A. T.; Gabdrakhmanov, Al T.

    2017-01-01

    This paper proposes an efficient method of plasma purification of metal surfaces before applying coatings or the product finishing treatment. The plasma purification is performed in a steam-gas discharge with an aluminum anode and a liquid cathode.

  3. Elastomers bonded to metal surfaces seal electrochemical cells

    NASA Technical Reports Server (NTRS)

    Sherfey, J. M.

    1964-01-01

    A leakproof seal secondary cell containing alkaline electrolytes was developed by bonding an alkali-resistant elastomer, such as neoprene, to metal contact surfaces. Test results of several different elastomers strongly indicate the feasibility of this sealing method.

  4. Surface Attack on Metals in the Presence of Liquid Metals.

    DTIC Science & Technology

    1986-04-10

    Lo *stics Age y. DITiUTION STATEMENT A 4 C. St r fene TecN al forma on C iter b Cmeon tatzooe on7500 17. UPPLEMAR NOTES * D ~III 1473EENAR NOESINO O... metalI . is to be controlled, and this problem is covered more fully in the section on diffusion characteristics of alloy combinations. Reaction models on...antimony and arsenic are stable additions but bismuth 40 removal is rapid by an evaporation mechanism. Anti - mony provides a stronger creep resistant

  5. Permanent recording of light helicity on optically inactive metal surfaces.

    PubMed

    Wang, Jincheng; Guo, Chunlei

    2006-12-15

    We report on an unusual permanent recording of light helicity on optically achiral metals. Following a number of circularly polarized (CP) or elliptically polarized (EP) femtosecond laser pulses, well-defined periodic surface structures are found on metal surfaces. These surface structures show different orientation when formed by left CP/EP compared with right CP/EP light. The formation of these structures is attributed to the interference between the incident light and the excited surface plasmons. To our knowledge, this is the only phenomenon that can permanently record light helicity with an optically inactive material.

  6. Multilayer Relaxation and Surface Energies of Metallic Surfaces

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Rodriguez, Agustin M.; Ferrante, John

    1994-01-01

    The perpendicular and parallel multilayer relaxations of fcc (210) surfaces are studied using equivalent crystal theory (ECT). A comparison with experimental and theoretical results is made for AI(210). The effect of uncertainties in the input parameters on the magnitudes and ordering of surface relaxations for this semiempirical method is estimated. A new measure of surface roughness is proposed. Predictions for the multilayer relaxations and surface energies of the (210) face of Cu and Ni are also included.

  7. Nanoscale segregation at a metal surface

    NASA Astrophysics Data System (ADS)

    Igata, N.

    1996-03-01

    The properties of a surface are fundamentally controlled by the chemical composition of the nanoscale surface layer. Therefore nanoscale segregation at the surface is one of the most important problems in surface science and technology. The chemical analysis of the surface layer and the study of segregation have been developed by various methods, but mainly by AES and TOFAP since 0957-4484/7/1/003/img1. Surface segregation under irradiation is also an urgent problem to be solved and the same methods have been applied. In this paper, the results from TOFAP for segregation both under thermal equilibrium and under irradiation are introduced. As for theoretical aspects, both thermal segregation and segregation under irradiation are interpreted by atomistic theory.

  8. Method for producing highly reflective metal surfaces

    DOEpatents

    Arnold, J.B.; Steger, P.J.; Wright, R.R.

    1982-03-04

    The invention is a novel method for producing mirror surfaces which are extremely smooth and which have high optical reflectivity. The method includes depositing, by electrolysis, an amorphous layer of nickel on an article and then diamond-machining the resulting nickel surface to increase its smoothness and reflectivity. The machined nickel surface then is passivated with respect to the formation of bonds with electrodeposited nickel. Nickel then is electrodeposited on the passivated surface to form a layer of electroplated nickel whose inside surface is a replica of the passivated surface. The mandrel then may be-re-passivated and provided with a layer of electrodeposited nickel, which is then recovered from the mandrel providing a second replica. The mandrel can be so re-used to provide many such replicas. As compared with producing each mirror-finished article by plating and diamond-machining, the new method is faster and less expensive.

  9. How do energetic ions damage metallic surfaces?

    DOE PAGES

    Osetskiy, Yury N.; Calder, Andrew F.; Stoller, Roger E.

    2015-02-20

    Surface modification under bombardment by energetic ions observed under different conditions in structural and functional materials and can be either unavoidable effect of the conditions or targeted modification to enhance materials properties. Understanding basic mechanisms is necessary for predicting properties changes. The mechanisms activated during ion irradiation are of atomic scale and atomic scale modeling is the most suitable tool to study these processes. In this paper we present results of an extensive simulation program aimed at developing an understanding of primary surface damage in iron by energetic particles. We simulated 25 keV self-ion bombardment of Fe thin films withmore » (100) and (110) surfaces at room temperature. A large number of simulations, ~400, were carried out allow a statistically significant treatment of the results. The particular mechanism of surface damage depends on how the destructive supersonic shock wave generated by the displacement cascade interacts with the free surface. Three basic scenarios were observed, with the limiting cases being damage created far below the surface with little or no impact on the surface itself, and extensive direct surface damage on the timescale of a few picoseconds. In some instances, formation of large <100> vacancy loops beneath the free surface was observed, which may explain some earlier experimental observations.« less

  10. How do energetic ions damage metallic surfaces?

    SciTech Connect

    Osetskiy, Yury N.; Calder, Andrew F.; Stoller, Roger E.

    2015-02-20

    Surface modification under bombardment by energetic ions observed under different conditions in structural and functional materials and can be either unavoidable effect of the conditions or targeted modification to enhance materials properties. Understanding basic mechanisms is necessary for predicting properties changes. The mechanisms activated during ion irradiation are of atomic scale and atomic scale modeling is the most suitable tool to study these processes. In this paper we present results of an extensive simulation program aimed at developing an understanding of primary surface damage in iron by energetic particles. We simulated 25 keV self-ion bombardment of Fe thin films with (100) and (110) surfaces at room temperature. A large number of simulations, ~400, were carried out allow a statistically significant treatment of the results. The particular mechanism of surface damage depends on how the destructive supersonic shock wave generated by the displacement cascade interacts with the free surface. Three basic scenarios were observed, with the limiting cases being damage created far below the surface with little or no impact on the surface itself, and extensive direct surface damage on the timescale of a few picoseconds. In some instances, formation of large <100> vacancy loops beneath the free surface was observed, which may explain some earlier experimental observations.

  11. Lipophilic super-absorbent polymer gels as surface cleaners for oil and grease from metal and non-metal surfaces

    USDA-ARS?s Scientific Manuscript database

    The objective of this research is to develop a new cleaning technology based on lipophilic super-absorbent swelling gels for the removal of oil, grease and particulate matters from metal and non-metal surfaces. It is desired that the cleaner is in solid form and is VOC-exempt, HAP-free, non-toxic, n...

  12. Characterisation of the surface of freshly prepared precious metal catalysts.

    PubMed

    Parker, Stewart F; Adroja, Devashibhai; Jiménez-Ruiz, Mónica; Tischer, Markus; Möbus, Konrad; Wieland, Stefan D; Albers, Peter

    2016-07-14

    A combination of electron microscopy, X-ray and neutron spectroscopies and computational methods has provided new insights into the species present on the surface of freshly prepared precious metal catalysts. The results show that in all cases, at least half of the surface is metallic or nearly so, with the remainder covered by oxygen, largely as hydroxide. Water is also present and is strongly held; weeks of pumping under high vacuum is insufficient to remove it. The hydroxyls are reactive as shown by their reaction with or displacement by CO and can be removed by hydrogenation. This clearly has implications for how precious metal catalysts are activated after preparation.

  13. Single crystal metal wedges for surface acoustic wave propagation

    DOEpatents

    Fisher, Edward S.

    1982-01-01

    An ultrasonic testing device has been developed to evaluate flaws and inhomogeneities in the near-surface region of a test material. A metal single crystal wedge is used to generate high frequency Rayleigh surface waves in the test material surface by conversion of a slow velocity, bulk acoustic mode in the wedge into a Rayleigh wave at the metal-wedge test material interface. Particular classes of metals have been found to provide the bulk acoustic modes necessary for production of a surface wave with extremely high frequency and angular collimation. The high frequency allows flaws and inhomogeneities to be examined with greater resolution. The high degree of angular collimation for the outgoing ultrasonic beam permits precision angular location of flaws and inhomogeneities in the test material surface.

  14. Single crystal metal wedges for surface acoustic wave propagation

    DOEpatents

    Fisher, E.S.

    1980-05-09

    An ultrasonic testing device has been developed to evaluate flaws and inhomogeneities in the near-surface region of a test material. A metal single crystal wedge is used to generate high frequency Rayleigh surface waves in the test material surface by conversion of a slow velocity, bulk acoustic mode in the wedge into a Rayleigh wave at the metal-wedge test material interface. Particular classes of metals have been found to provide the bulk acoustic modes necessary for production of a surface wave with extremely high frequency and angular collimation. The high frequency allows flaws and inhomogeneities to be examined with greater resolution. The high degree of angular collimation for the outgoing ultrasonic beam permits precision angular location of flaws and inhomogeneities in the test material surface.

  15. Surface and subsurface hydrogen: adsorption properties on transition metals and near-surface alloys.

    PubMed

    Greeley, Jeff; Mavrikakis, Manos

    2005-03-03

    Periodic, self-consistent DFT-GGA calculations are used to study the thermochemical properties of both surface and subsurface atomic hydrogen on a variety of pure metals and near-surface alloys (NSAs). For surface hydrogen on pure metals, calculated site preferences, adsorption geometries, vibrational frequencies, and binding energies are reported and are found to be in good agreement with available experimental data. On NSAs, defined as alloys wherein a solute is present near the surface of a host metal in a composition different from the bulk composition, surface hydrogen generally binds more weakly than it binds to the pure-metal components composing the alloys. Some of the NSAs even possess the unusual property of binding hydrogen as weakly as the noble metals while, at the same time, dissociating H(2) much more easily. On both NSAs and pure metals, formation of surface hydrogen is generally exothermic with respect to H(2)(g). In contrast, formation of subsurface hydrogen is typically endothermic with respect to gas-phase H(2) (the only exception to this general statement is found for pure Pd). As with surface H, subsurface H typically binds more weakly to NSAs than to the corresponding pure-metal components of the alloys. The diffusion barrier for hydrogen from surface to subsurface sites, however, is usually lower on NSAs compared to the pure-metal components, suggesting that population of subsurface sites may occur more rapidly on NSAs.

  16. MEED studies of thin metal film covered semiconductor surfaces

    NASA Astrophysics Data System (ADS)

    Shimaoka, G.

    1991-06-01

    Results of observations of thin metal films deposited on clean surfaces of semiconductors, such as Si, GaAs and GaP, in the early stage of deposition in UHV, are reported with particular emphasis on in-situ MEED observations at 1-5 kV using a grazing angle of incidence. Various atomic rearrangements and reconstructions due to thin metal deposits were observed, for example: 2 × 1 and 4 × 5 reconstruction of Ni on a clean Si(110)16 × 2 surface, and formation of a one-dimensional lattice of Ag on a coplanar plane of GaAs (001) and GaP (001) and (011). These results are also discussed in terms of surface structures with special emphasis on the early stages of metal deposition and on the metal/semiconductor interface.

  17. A review of metallic, ceramic and surface-treated metals used for bearing surfaces in human joint replacements.

    PubMed

    Dearnley, P A

    1999-01-01

    A review of established and advanced materials used for the bearing surfaces of total hip replacements (THRs), their standards, methods of manufacture and corrosion testing is presented. Some account is also taken of parallel developments in femoral components used in total knee replacements (TKRs). Metallic, ceramic and surface-modified metallic materials are separately reviewed, but wherever possible common practices are collated. Coated implant bearing surfaces are in an advanced state of development and some designs are receiving clinical evaluation. To date, however, no standard methods of manufacturing and testing these materials have been agreed. Accordingly, corrosion and other key quality test methods suitable for surface-modified implant bearing materials are reviewed.

  18. Modulation of photoacoustic signal generation from metallic surfaces

    PubMed Central

    Mitcham, Trevor; Homan, Kimberly; Frey, Wolfgang; Chen, Yun-Sheng; Emelianov, Stanislav; Hazle, John

    2013-01-01

    Abstract. The ability to image metallic implants is important for medical applications ranging from diagnosis to therapy. Photoacoustic (PA) imaging has been recently pursued as a means to localize metallic implants in soft tissue. The work presented herein investigates different mechanisms to modulate the PA signal generated by macroscopic metallic surfaces. Wires of five different metals are tested to simulate medical implants/tools, while surface roughness is altered or physical vapor deposition (PVD) coatings are added to change the wires’ overall optical absorption. PA imaging data of the wires are acquired at 970 nm. Results indicate that PA signal generation predominately occurs in a wire’s metallic surface and not its aqueous surroundings. PA signal generation is similar for all metals tested, while addition of PVD coatings offers significant modulations (i.e., 4-dB enhancement and 26-dB reduction achieved) in PA signal generation. Results also suggest that PA signal increases with increasing surface roughness. Different coating and roughness schemes are then successfully utilized to generate spatial PA signal patterns. This work demonstrates the potential of surface modifications to enhance or reduce PA signal generation to permit improved PA imaging of implants/tools (i.e., providing location/orientation information) or to allow PA imaging of surrounding tissue. PMID:23652344

  19. Modulation of photoacoustic signal generation from metallic surfaces

    NASA Astrophysics Data System (ADS)

    Mitcham, Trevor; Homan, Kimberly; Frey, Wolfgang; Chen, Yun-Sheng; Emelianov, Stanislav; Hazle, John; Bouchard, Richard

    2013-05-01

    The ability to image metallic implants is important for medical applications ranging from diagnosis to therapy. Photoacoustic (PA) imaging has been recently pursued as a means to localize metallic implants in soft tissue. The work presented herein investigates different mechanisms to modulate the PA signal generated by macroscopic metallic surfaces. Wires of five different metals are tested to simulate medical implants/tools, while surface roughness is altered or physical vapor deposition (PVD) coatings are added to change the wires' overall optical absorption. PA imaging data of the wires are acquired at 970 nm. Results indicate that PA signal generation predominately occurs in a wire's metallic surface and not its aqueous surroundings. PA signal generation is similar for all metals tested, while addition of PVD coatings offers significant modulations (i.e., 4-dB enhancement and 26-dB reduction achieved) in PA signal generation. Results also suggest that PA signal increases with increasing surface roughness. Different coating and roughness schemes are then successfully utilized to generate spatial PA signal patterns. This work demonstrates the potential of surface modifications to enhance or reduce PA signal generation to permit improved PA imaging of implants/tools (i.e., providing location/orientation information) or to allow PA imaging of surrounding tissue.

  20. Metal-Induced Reconstructions on Semiconductor Surfaces

    NASA Astrophysics Data System (ADS)

    Li, Lian

    1995-01-01

    Scanning tunneling microscopy (STM) has been used to study the surface morphology induced by In, Ga, and Sn overlayers on Si(100) and Si(311) surfaces. STM and low-energy electron microscopy (LEEM) were used to study the surface morphology of Pb overlayer grown on Si(100) -(2 x 1). Reconstructions on clean alpha -SiC(0001) and alpha-SiC(0001) surfaces and those induced by deposition of Ti were also studied. We found that deposition of In produced step bunching and faceting on vicinal Si(100) surface. At coverages >=1 ML, the original step direction of (01 1) changed to a zig-zag along low-index (010) and (001) directions, and the bunched steps became {130} facets. At annealing temperatures >=550^ circC, the {130} facets disappeared and the bunched steps were restored with meandering step directions. For the case of Pb adsorption on Si(100)-(2 x 1) surface, surface reconstructions of (2 x 2), c(4 x 8), (2 x 1), and c(4 x 4) were observed as Pb coverages increased from 0.5 to 1.5 ML. After the appearance of the c(4 x 4) phase, Pb islands with threefold-symmetric (111) orientation were observed on the twofold or fourfold-symmetric Si(100) surface. Both Sn and Ga adsorption on Si(100)-(2 x 1) and Si(311)-(3 x 2) surfaces induced complex surface morphologies when the coverage exceeded 1 ML. Rectangular and square depressions shaped like inverted pyramids were formed at Ga coverage above 1 ML. The walls of the inverted pyramids were (311). Deposition of Sn on Si(100) at coverages exceeding 2 ML also produced (311) facets, but they formed the faces of long parallel and orthogonal prisms, giving rise to a large scale maze-like structure on the surface. Deposition of Ga on the Si(311)-(3 x 2) surface produced ordered (211) and (611) facets at coverage above 1 ML. On the other hand, deposition of Sn on Si(311)-(3 x 2) did not produce any facet. Instead, layer-by-layer growth of (1 x 1) pseudomorphic Sn was observed on the Si(311) surface up to 6 ML. Ge growth on Si(100

  1. Sulfur-induced structural motifs on copper and gold surfaces

    NASA Astrophysics Data System (ADS)

    Walen, Holly

    The interaction of sulfur with copper and gold surfaces plays a fundamental role in important phenomena that include coarsening of surface nanostructures, and self-assembly of alkanethiols. Here, we identify and analyze unique sulfur-induced structural motifs observed on the low-index surfaces of these two metals. We seek out these structures in an effort to better understand the fundamental interactions between these metals and sulfur that lends to the stability and favorability of metal-sulfur complexes vs. chemisorbed atomic sulfur. We choose very specific conditions: very low temperature (5 K), and very low sulfur coverage (≤ 0.1 monolayer). In this region of temperature-coverage space, which has not been examined previously for these adsorbate-metal systems, the effects of individual interactions between metals and sulfur are most apparent and can be assessed extensively with the aid of theory and modeling. Furthermore, at this temperature diffusion is minimal and relatively-mobile species can be isolated, and at low coverage the structures observed are not consumed by an extended reconstruction. The primary experimental technique is scanning tunneling microscopy (STM). The experimental observations presented here---made under identical conditions---together with extensive DFT analyses, allow comparisons and insights into factors that favor the existence of metal-sulfur complexes, vs. chemisorbed atomic sulfur, on metal terraces. We believe this data will be instrumental in better understanding the complex phenomena occurring between the surfaces of coinage metals and sulfur.

  2. Light scattering by surface acoustic waves on corrugated metal surfaces

    SciTech Connect

    Robertson, W.M.; Grimsditch, M. ); Moretti, A.L.; Kaufman, R.G.; Hulse, G.R. ); Fullerton, E.; Schuller, I.K. )

    1990-03-15

    We report the results of a Brillouin-scattering study of corrugated Ag surfaces. The corrugation plays a dramatic role in the wave-vector--selection rules governing coupling to surface phonons, and this effect is substantially different when the effective wave vector of the surface corrugation is collinear or perpendicular to the scattering plane. In processes that involve the grating wave vector, we show that the coupling mechanism between light and phonons is governed by surface plasmons which introduce a new scattering interaction with unusual polarization features in the Brillouin-scattering process.

  3. Method for producing highly reflective metal surfaces

    DOEpatents

    Arnold, Jones B.; Steger, Philip J.; Wright, Ralph R.

    1983-01-01

    The invention is a novel method for producing mirror surfaces which are extremely smooth and which have high optical reflectivity. The method includes electrolessly depositing an amorphous layer of nickel on an article and then diamond-machining the resulting nickel surface to increase its smoothness and reflectivity. The machined nickel surface then is passivated with respect to the formation of bonds with electrodeposited nickel. Nickel then is electrodeposited on the passivated surface to form a layer of electroplated nickel whose inside surface is a replica of the passivated surface. The electroplated nickel layer then is separated from the passivated surface. The mandrel then may be re-passivated and provided with a layer of electrodeposited nickel, which is then recovered from the mandrel providing a second replica. The mandrel can be so re-used to provide many such replicas. As compared with producing each mirror-finished article by plating and diamond-machining, the new method is faster and less expensive.

  4. Interaction of Water with Metal Surfaces

    DTIC Science & Technology

    1994-02-18

    Government This document has been approved for public release and sale; its distribution is unlimited 94-06693 94 2 28 1104 IIIi Ih im1lii P Best...label w) To begin, consider a perfect crystal surface in which the basic vectors of the lattice are a, and a 2. Next consider a point particle p at r...pp, zp) where zp is the perpendicular distance above the surface and pp is the projection of rp onto the surface plane. The label p stands for 0 or

  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. Resonance Fluorescence of Many Interacting Adatoms at a Metal Surface.

    DTIC Science & Technology

    1983-06-01

    a series of experiments in which the fluores - cence of an excited atom or molecule at a fixed distance from a metal surface (gold, silver and cooper...Theodore E. Madey Surface Chemistry Section Dr. Chia -wel Woo Department of Commerce Department of Physics National Bureau of Standards Northwestern

  7. Surface Plasmon Resonance Evaluation of Colloidal Metal Aerogel Filters

    NASA Technical Reports Server (NTRS)

    Smith, David D.; Sibille, Laurent; Cronise, Raymond J.; Noever, David A.

    1997-01-01

    Surface plasmon resonance imaging has in the past been applied to the characterization of thin films. In this study we apply the surface plasmon technique not to determine macroscopic spatial variations but rather to determine average microscopic information. Specifically, we deduce the dielectric properties of the surrounding gel matrix and information concerning the dynamics of the gelation process from the visible absorption characteristics of colloidal metal nanoparticles contained in aerogel pores. We have fabricated aerogels containing gold and silver nanoparticles. Because the dielectric constant of the metal particles is linked to that of the host matrix at the surface plasmon resonance, any change 'in the dielectric constant of the material surrounding the metal nanoparticles results in a shift in the surface plasmon wavelength. During gelation the surface plasmon resonance shifts to the red as the average or effective dielectric constant of the matrix increases. Conversely, formation of an aerogel or xerogel through supercritical extraction or evaporation of the solvent produces a blue shift in the resonance indicating a decrease in the dielectric constant of the matrix. From the magnitude of this shift we deduce the average fraction of air and of silica in contact with the metal particles. The surface area of metal available for catalytic gas reaction may thus be determined.

  8. Surface Plasmon Resonance Evaluation of Colloidal Metal Aerogel Filters

    NASA Technical Reports Server (NTRS)

    Smith, David D.; Sibille, Laurent; Cronise, Raymond J.; Noever, David A.

    1997-01-01

    Surface plasmon resonance imaging has in the past been applied to the characterization of thin films. In this study we apply the surface plasmon technique not to determine macroscopic spatial variations but rather to determine average microscopic information. Specifically, we deduce the dielectric properties of the surrounding gel matrix and information concerning the dynamics of the gelation process from the visible absorption characteristics of colloidal metal nanoparticles contained in aerogel pores. We have fabricated aerogels containing gold and silver nanoparticles. Because the dielectric constant of the metal particles is linked to that of the host matrix at the surface plasmon resonance, any change 'in the dielectric constant of the material surrounding the metal nanoparticles results in a shift in the surface plasmon wavelength. During gelation the surface plasmon resonance shifts to the red as the average or effective dielectric constant of the matrix increases. Conversely, formation of an aerogel or xerogel through supercritical extraction or evaporation of the solvent produces a blue shift in the resonance indicating a decrease in the dielectric constant of the matrix. From the magnitude of this shift we deduce the average fraction of air and of silica in contact with the metal particles. The surface area of metal available for catalytic gas reaction may thus be determined.

  9. Stress induced half-metallicity in surface defected germanium nanowires.

    PubMed

    Sk, Mahasin Alam; Ng, Man-Fai; Yang, Shuo-Wang; Lim, Kok Hwa

    2012-01-21

    Germanium nanowires (GeNWs) with single, double, quadruple and octuple surface dangling bonds (SDBs) are investigated using density-functional-theory calculations. We show that single SDB defected GeNWs remain semiconducting as their non-defected form while double or multiple SDB defects result in either semiconducting or metallic GeNWs, depending on the defect's locations on the surface. More importantly, we show that the electronic properties of surface defected GeNWs can also be fine-tuned by applying tensile and compressive strains. Upon the right loading, the surface defected GeNWs become half-metallic. In addition, we determine that the surface defected GeNWs can be classified into three classes: (1) GeNWs with zero magnetic moment, which are either metallic or semiconducting; (2) GeNWs with net magnetic moments equal to the number of SDBs, which are semiconducting with distinct spin-up and spin-down configurations; and (3) GeNWs with net magnetic moments significantly lower than the number of SDBs. We also find that only the defected GeNWs that fall under (3) are potentially half-metallic. Our results predict that half-metallic GeNWs can be obtained via engineering of the surface defects and the structures without the presence of impurity dopants.

  10. Leidenfrost point reduction on micropatterned metallic surfaces.

    PubMed

    del Cerro, Daniel Arnaldo; Marín, Alvaro G; Römer, Gertwillem R B E; Pathiraj, B; Lohse, Detlef; Huis in 't Veld, Albertus J

    2012-10-23

    Droplets are able to levitate when deposited over a hot surface exceeding a critical temperature. This is known as the Leidenfrost effect. This phenomenon occurs when the surface is heated above the so-called Leidenfrost point (LFP), above which the vapor film between the droplet and hot surface is able to levitate the droplet. Such a critical temperature depends on several factors. One of the most studied parameters has been the surface roughness. Almost all of the experimental studies in the literature have concluded that the LFP increases with the roughness. According to these results, it seems that the roughness is detrimental for the stability of the vapor film. In contrast with these results, we present here a micropatterned surface that significantly reduces the LFP. The temperature increase, relative to the boiling point, required to reach the LFP is 70% lower than that on the flat surface. The reasons for such an effect are qualitatively and quantitatively discussed with a simple semiempirical model. This result can be relevant to save energy in applications that take advantage of the Leidenfrost effect for drop control or drag reduction.

  11. Femtosecond laser-induced electronic plasma at metal surface

    SciTech Connect

    Chen Zhaoyang; Mao, Samuel S.

    2008-08-04

    We develop a theoretical analysis to model plasma initiation at the early stage of femtosecond laser irradiation of metal surfaces. The calculation reveals that there is a threshold intensity for the formation of a microscale electronic plasma at the laser-irradidated metal surface. As the full width at half maximum of a laser pulse increases from 15 to 200 fs, the plasma formation threshold decreases by merely about 20%. The dependence of the threshold intensity on laser pulse width can be attributed to laser-induced surface electron emission, in particular due to the effect of photoelectric effect.

  12. Self-excitation of Rydberg atoms at a metal surface

    NASA Astrophysics Data System (ADS)

    Bordo, V. G.

    2017-08-01

    The novel effect of self-excitation of an atomic beam propagating above a metal surface is predicted and a theory is developed. Its underlying mechanism is positive feedback provided by the reflective surface for the atomic polarization. Under certain conditions the atomic beam flying in the near field of the metal surface acts as an active device that supports sustained atomic dipole oscillations, which generate, in their turn, an electromagnetic field. This phenomenon does not exploit stimulated emission and therefore does not require population inversion in atoms. An experiment with Rydberg atoms in which this effect should be most pronounced is proposed and the necessary estimates are given.

  13. Graphene on weakly interacting metals: Dirac states versus surface states

    NASA Astrophysics Data System (ADS)

    Jolie, Wouter; Craes, Fabian; Busse, Carsten

    2015-03-01

    We investigate the interplay between graphene and different, weakly interacting metal substrates by measuring the local density of states of the surface with scanning tunneling spectroscopy. Energy-resolved Friedel oscillations, confined states, and a prominent signal in point spectra are found after intercalating several monolayers of silver between graphene and Ir(111) and correspond to the shifted surface state of silver. These features outweigh spectroscopic signatures of graphene, which are retrieved when the amount of silver is reduced to one monolayer. Hence, suppressing the surface states of the metal substrate enhances the sensitivity to the Dirac states of quasi-free-standing graphene.

  14. Inelastic electron tunneling into graphene nanostructures on a metal surface

    NASA Astrophysics Data System (ADS)

    Néel, N.; Steinke, C.; Wehling, T. O.; Kröger, J.

    2017-04-01

    Wrinkles and blisters of graphene on Ir(111) give rise to remarkably high signals in inelastic electron tunneling spectroscopy due to graphene phonons. Spatially resolved spectra unravel the gradual increase of the graphene phonon signatures with progressive delamination of graphene from the metal surface. Spectroscopy of the Ir(111) surface resonance evidences that the graphene-metal hybridization is efficiently reduced in wrinkles and blisters. A high phonon density of states favors the observation of phonons with wave vectors near the M ¯ point of the surface Brillouin zone.

  15. Stimulated emission of surface plasmons by electron tunneling in metal-barrier-metal structures

    NASA Technical Reports Server (NTRS)

    Siu, D. P.; Gustafson, T. K.

    1978-01-01

    It is shown that correlation currents arising from the superposition of pairs of states on distinct sides of a potential barrier in metal-barrier-metal structures can result in inelastic tunneling through the emission of surface plasmons. Net gain of an externally excited plasmon field is possible.

  16. Activation of carbon dioxide on metal and metal oxide surfaces

    SciTech Connect

    Tan, C.D.; Chuang, S.S.C.

    1995-12-31

    The environmental concern about the impact of CO{sub 2} has grown recently due to its rapidly increasing concentration. Deforestation strongly affects the natural reduction of CO{sub 2} by water into carbohydrates by photosynthesis. Industrial utilization of CO{sub 2} by heterogeneous catalytic reactions can be one of the effective ways to cut the CO{sub 2} level. The first step in catalytic reaction of CO{sub 2} is the adsorption. The objective of this study is to investigate the adsorption of CO{sub 2} on the Rh/Al{sub 2}O{sub 3} surfaces. Rh is selected for this study because of its unique activity to catalyze a number of CO{sub 2} related reactions. In situ infrared results show that CO{sub 2} adsorbed on the alumina oxide support as bidentate carbonate and non-coordinated carbon which are the dominant species during the CO{sub 2} adsorption.

  17. Surface Complexation Modelling in Metal-Mineral-Bacteria Systems

    NASA Astrophysics Data System (ADS)

    Johnson, K. J.; Fein, J. B.

    2002-12-01

    The reactive surfaces of bacteria and minerals can determine the fate, transport, and bioavailability of aqueous heavy metal cations. Geochemical models are instrumental in accurately accounting for the partitioning of the metals between mineral surfaces and bacteria cell walls. Previous research has shown that surface complexation modelling (SCM) is accurate in two-component systems (metal:mineral and metal:bacteria); however, the ability of SCMs to account for metal distribution in mixed metal-mineral-bacteria systems has not been tested. In this study, we measure aqueous Cd distributions in water-bacteria-mineral systems, and compare these observations with predicted distributions based on a surface complexation modelling approach. We measured Cd adsorption in 2- and 3-component batch adsorption experiments. In the 2-component experiments, we measured the extent of adsorption of 10 ppm aqueous Cd onto either a bacterial or hydrous ferric oxide sorbent. The metal:bacteria experiments contained 1 g/L (wet wt.) of B. subtilis, and were conducted as a function of pH; the metal:mineral experiments were conducted as a function of both pH and HFO content. Two types of 3-component Cd adsorption experiments were also conducted in which both mineral powder and bacteria were present as sorbents: 1) one in which the HFO was physically but not chemically isolated from the system using sealed dialysis tubing, and 2) others where the HFO, Cd and B. subtilis were all in physical contact. The dialysis tubing approach enabled the direct determination of the concentration of Cd on each sorbing surface, after separation and acidification of each sorbent. The experiments indicate that both bacteria and mineral surfaces can dominate adsorption in the system, depending on pH and bacteria:mineral ratio. The stability constants, determined using the data from the 2-component systems, along with those for other surface and aqueous species in the systems, were used with FITEQL to

  18. Atomic-scale simulation of adhesion between metallic surfaces

    SciTech Connect

    Taylor, P.A.

    1990-01-01

    We have performed MD simulations of adhesive phenomena, on an atomic scale, between metals possessing both smooth and stepped-surfaces. Studies of adhesion between identical metals, consisting of either Au, Cu, or Ni, with (001) or (111) orientations, reveal the existence of adhesive avalanches as the bodies are brought to within a critical separation ({approximately}2 {angstrom}). That is, as the surfaces approach one another, one or both surface layers becomes unstable, and abruptly moves toward the other. This signals a transition from an initial system with two distinct surfaces to one possessing no identifiable surfaces. The presence of adhesive avalanches will pose difficulties in determining adhesive forces and energies by means of atomic force microscopy at sub-nanometer separations of probe tip and sample surface. 7 refs., 3 figs.

  19. Surface plasmon dispersion analysis in the metal-oxide-metal tunnel diode

    NASA Technical Reports Server (NTRS)

    Donohue, J. F.; Wang, E. Y.

    1987-01-01

    A detailed model of surface plasmon dispersion in the metal-oxide-metal tunnel diode is presented in order to clarify the spectral emission from this diode. The model predicts the location of the spectral peaks and the emission between the peaks by considering the effects of retardation on the surface plasmon. A nonradiative mode is found to play a major role in the transition from the visible to UV peaks in the diode spectra.

  20. Isolation and characterization of bacteria resistant to metallic copper surfaces.

    PubMed

    Santo, Christophe Espírito; Morais, Paula Vasconcelos; Grass, Gregor

    2010-03-01

    Metallic copper alloys have recently attracted attention as a new antimicrobial weapon for areas where surface hygiene is paramount. Currently it is not understood on a molecular level how metallic copper kills microbes, but previous studies have demonstrated that a wide variety of bacteria, including Escherichia coli, Staphylococcus aureus, and Clostridium difficile, are inactivated within minutes or a few hours of exposure. In this study, we show that bacteria isolated from copper alloy coins comprise strains that are especially resistant against the toxic properties exerted by dry metallic copper surfaces. The most resistant of 294 isolates were Gram-positive staphylococci and micrococci, Kocuria palustris, and Brachybacterium conglomeratum but also included the proteobacterial species Sphingomonas panni and Pseudomonas oleovorans. Cells of some of these bacterial strains survived on copper surfaces for 48 h or more. Remarkably, when these dry-surface-resistant strains were exposed to moist copper surfaces, resistance levels were close to those of control strains and MICs for copper ions were at or below control strain levels. This suggests that mechanisms conferring resistance against dry metallic copper surfaces in these newly isolated bacterial strains are different from well-characterized copper ion detoxification systems. Furthermore, staphylococci on coins did not exhibit increased levels of resistance to antibiotics, arguing against coselection with copper surface resistance traits.

  1. Anharmonic surface vibrations in photoemission from alkali metals

    SciTech Connect

    Wertheim, G.K.; Riffe, D.M.; Citrin, P.H. )

    1994-01-15

    The phonon widths of outermost core-electron photoemission spectra from (110)-oriented overlayers of Na, K, and Rb metals show the expected Debye behavior for the bulk atoms, but significant deviations for the surface atoms. The data indicate a softening of the surface vibrational mode above 200 K. This effect, which is weak in Na but strong in K and Rb, demonstrates that the vibrational mode normal to the surface is anharmonic.

  2. Ice nanoclusters at hydrophobic metal surfaces.

    PubMed

    Michaelides, Angelos; Morgenstern, Karina

    2007-08-01

    Studies of the structure of supported water clusters provide a means for obtaining a rigorous molecular-scale description of the initial stages of heterogeneous ice nucleation: a process of importance to fields as diverse as atmospheric chemistry, astrophysics and biology. Here, we report the observation and characterization of metal-supported water hexamers and a family of hydrated nanoclusters--heptamers, octamers and nonamers--through a combination of low-temperature scanning tunnelling microscopy experiments and first-principles electronic-structure calculations. Aside from achieving unprecedented resolution of the cyclic water hexamer--the so-called smallest piece of ice--we identify and explain a hitherto unknown competition between the ability of water molecules to simultaneously bond to a substrate and to accept hydrogen bonds. This competition also rationalizes previous structure predictions for water clusters on other substrates.

  3. Surface tension of liquid metals and alloys--recent developments.

    PubMed

    Egry, I; Ricci, E; Novakovic, R; Ozawa, S

    2010-09-15

    Surface tension measurements are a central task in the study of surfaces and interfaces. For liquid metals, they are complicated by the high temperatures and the consequently high reactivity characterising these melts. In particular, oxidation of the liquid surface in combination with evaporation phenomena requires a stringent control of the experimental conditions, and an appropriate theoretical treatment. Recently, much progress has been made on both sides. In addition to improving the conventional sessile drop technique, new containerless methods have been developed for surface tension measurements. This paper reviews the experimental progress made in the last few years, and the theoretical framework required for modelling and understanding the relevant physico-chemical surface phenomena.

  4. Light-induced binding of metal nanoparticles via surface plasmons

    NASA Astrophysics Data System (ADS)

    Chan, K. L.; Zheng, M. J.; Yu, K. W.

    2010-03-01

    Recently, nanomachines based on the interaction of nanosize objects with nanostructrued surfaces have attracted much attention. In this work, we study theoretically the light-induced binding forces between a metallic nanosphere and a planar structure, and also between nanoparticles in a diatomic plamonic chain of shelled and unshelled metallic nanoparticles placed alternatively. These forces are calculated by Bergman-Milton spectral representation and multiple image methods within the long wavelength limit. When we tune the incident frequency to the surface plasmon resonant frequency, a stable local minimum in the potential energy is found. It signifies a binding between nanoparticles (nanostructures), which indicates a possible stable structure of the metallic clusters. Such binding is caused by the excitation of collective plasmon modes, which depends on the interparticle distances. This study has potential applications in plasmonic waveguides and colloidal metallic clusters on the nanoscales.

  5. Emerging applications of liquid metals featuring surface oxides.

    PubMed

    Dickey, Michael D

    2014-11-12

    Gallium and several of its alloys are liquid metals at or near room temperature. Gallium has low toxicity, essentially no vapor pressure, and a low viscosity. Despite these desirable properties, applications calling for liquid metal often use toxic mercury because gallium forms a thin oxide layer on its surface. The oxide interferes with electrochemical measurements, alters the physicochemical properties of the surface, and changes the fluid dynamic behavior of the metal in a way that has, until recently, been considered a nuisance. Here, we show that this solid oxide "skin" enables many new applications for liquid metals including soft electrodes and sensors, functional microcomponents for microfluidic devices, self-healing circuits, shape-reconfigurable conductors, and stretchable antennas, wires, and interconnects.

  6. Emerging Applications of Liquid Metals Featuring Surface Oxides

    PubMed Central

    2014-01-01

    Gallium and several of its alloys are liquid metals at or near room temperature. Gallium has low toxicity, essentially no vapor pressure, and a low viscosity. Despite these desirable properties, applications calling for liquid metal often use toxic mercury because gallium forms a thin oxide layer on its surface. The oxide interferes with electrochemical measurements, alters the physicochemical properties of the surface, and changes the fluid dynamic behavior of the metal in a way that has, until recently, been considered a nuisance. Here, we show that this solid oxide “skin” enables many new applications for liquid metals including soft electrodes and sensors, functional microcomponents for microfluidic devices, self-healing circuits, shape-reconfigurable conductors, and stretchable antennas, wires, and interconnects. PMID:25283244

  7. Method for producing functionally graded nanocrystalline layer on metal surface

    DOEpatents

    Ajayi, Oyelayo O.; Hershberger, Jeffrey G.

    2010-03-23

    An improved process for the creation or formation of nanocrystalline layers on substrates' surfaces is provided. The process involves "prescuffing" the surface of a substrate such as a metal by allowing friction to occur on the surface by a load-bearing entity making rubbing contact and moving along and on the substrate's surface. The "prescuffing" action is terminated when the coefficient of friction between the surface and the noise is rising significantly. Often, the significant rise in the coefficient of friction is signaled by a change in pitch of the scuffing action sound emanating from the buffeted surface. The "prescuffing" gives rise to a harder and smoother surface which withstands better any inadequate lubrication that may take place when the "prescuffed" surface is contacted by other surfaces.

  8. Surface phonons on Al(111) surface covered by alkali metals

    NASA Astrophysics Data System (ADS)

    Rusina, G. G.; Eremeev, S. V.; Borisova, S. D.; Sklyadneva, I. Yu.; Chulkov, E. V.

    2005-06-01

    We investigated the vibrational and structural properties of the Al(111)-(3×3)R30°-AM (AM=Na,K,Li) adsorbed systems using interaction potentials from the embedded-atom method. The surface relaxation, surface phonon dispersion, and polarization of vibrational modes for the alkali adatoms and the substrate atoms as well as the local density of states are discussed. Our calculated structural parameters are in close agreement with experimental and ab initio results. The obtained vibrational frequencies compare fairly well with the available experimental data.

  9. Method for the decontamination of metallic surfaces

    DOEpatents

    Purohit, Ankur; Kaminski, Michael D.; Nunez, Luis

    2003-01-01

    A method of decontaminating a radioactively contaminated oxide on a surface. The radioactively contaminated oxide is contacted with a diphosphonic acid solution for a time sufficient to dissolve the oxide and subsequently produce a precipitate containing most of the radioactive values. Thereafter, the diphosphonic solution is separated from the precipitate. HEDPA is the preferred diphosphonic acid and oxidizing and reducing agents are used to initiate precipitation. SFS is the preferred reducing agent.

  10. Enrichment of metals in the surface sediments of Sapanca Lake

    SciTech Connect

    Bakan, G.; Balkas, T.I.

    1999-01-01

    A comprehensive lake sediment study was performed on the Sapanca Lake of Turkey in which certain metal analyses were conducted using inductively coupled plasma atomic emission spectroscopy. The purpose of the study was to find the enrichment of metals in the surface sediments of Sapanca Lake. A method, namely, the index of geoaccumulation, was used to define the degree of anthropogenic pollution in the Sapanca Lake basin. Results of the geoaccumulation index indicate that only enrichments of trace metals, cadmium, and lead are found.

  11. Structure and bonding between an aryl group and metal surfaces

    SciTech Connect

    Jiang, Deen; Sumpter, Bobby G; Dai, Sheng

    2006-01-01

    Modifying solid surfaces with aryl groups has many potential applications. Using first principles density functional theory methods, we investigated the trend of the structure and bonding of the phenyl group (C6H5, the simplest aryl group) on selected transition metals across the periodic table. We found that the bond between C6H5 and metal surfaces is chemical in nature. Decreasing bond strength is found from left to right, concurrent with a switching of the preferred orientation for C6H5 from the flat-lying configuration to the upright configuration. This switching is attributed to the increasing of d-electrons, i.e., early transition metals, lacking d-electrons, favor the carbon-metal -bond and therefore the flat-lying configuration, while late transition metals rich in d-electrons prefer the carbon-metal -bond and thus the upright fashion. C6H5 is also found to undergo ]-dehydrogenation on early transition metals. This work invites further theoretical and experimental researches on the aryl-solid interface.

  12. Carbide and carbonitride surface treatment method for refractory metals

    DOEpatents

    Meyer, G.A.; Schildbach, M.A.

    1996-12-03

    A carbide and carbonitride surface treatment method for refractory metals is provided, in steps including, heating a part formed of boron, chromium, hafnium, molybdenum, niobium, tantalum, titanium, tungsten or zirconium, or alloys thereof, in an evacuated chamber and then introducing reaction gases including nitrogen and hydrogen, either in elemental or water vapor form, which react with a source of elemental carbon to form carbon-containing gaseous reactants which then react with the metal part to form the desired surface layer. Apparatus for practicing the method is also provided, in the form of a carbide and carbonitride surface treatment system including a reaction chamber, a source of elemental carbon, a heating subassembly and a source of reaction gases. Alternative methods of providing the elemental carbon and the reaction gases are provided, as well as methods of supporting the metal part, evacuating the chamber with a vacuum subassembly and heating all of the components to the desired temperature. 5 figs.

  13. Classification of surface structures on fine metallic wires

    NASA Astrophysics Data System (ADS)

    Bernabeu, E.; Sanchez-Brea, L. M.; Siegmann, P.; Martinez-Antón, J. C.; Gomez-Pedrero, J. A.; Wilkening, G.; Koenders, L.; Müller, F.; Hildebrand, M.; Hermann, H.

    2001-08-01

    In this report a classification of the main surface structures found on fine metallic wires is carried out (between ˜20 and 500 μm in diameter). For this, we have analyzed a series of wires of different metallic materials, diameters and production environments by scanning electron microscopy, atomic force microscopy, and confocal microscopy. A description and the images of the structures is given and, in addition, a nomenclature to be used by manufacturers, customers and researches is proposed. With this information the surface quality of fine metallic wires may be improved in a fabrication level. One of the objectives of this catalogue of defects is to serve as a basis for measuring the quality of the surface of the wires during the production process and the development of a measuring device for that purpose.

  14. Surface Integrity of Hard Metal Parts Machined by WEDM

    NASA Astrophysics Data System (ADS)

    Plaza, S.; Izquierdo, B.; Sanchez, J. A.; Ortega, N.; Ramos, J. M.

    2009-11-01

    Hard metal is characterised by having a extremely high hardness and high wear resistance, and those characteristics make difficult conventional machining. Electrical Discharge Machining (EDM) has become an attractive and feasible method for the manufacturing of precision hard metal tooling, and it is now an alternative to classical diamond grinding. This is due to the thermal nature of material removal mechanism in EDM, which is therefore independent on part hardness. This work pays attention to the analysis of surface integrity in wire EDM'ed hard metal parts. Damages on the machined surfaces have been characterised for different cutting regimes. Special attention has been paid to the heat affected zone, since it is in this zone where cracking mostly occurs. The study includes the analysis of the chemical composition of the affected layers. Additionally, the influence of successive trim cuts on surface roughness is addressed.

  15. Classical and quantum emitters near a metal surface

    NASA Astrophysics Data System (ADS)

    Mohammadi, Zahra; Kheirandish, Fardin

    2017-04-01

    The propagation of surface plasmon polaritons in an attenuating medium is investigated. The analytical calculations of the total electric-field Green’s tensor of a metal–dielectric interface structure are provided and novel explicit expressions for the Green’s tensor of a metal–dielectric interface are presented. The contribution of plasmons is obtained by evaluating the poles of the reflection coefficient for p-polarized waves incident on the metal interface. The emission pattern of a classical dipole located above the air/silver interface is studied. The relative intensity of the field to the field intensity in free space is studied for both normal and parallel orientations of the dipole. The quantum optical properties of a quantum emitter coupled to a metal surface are studied. Single photon emission is demonstrated for a quantum dot near a metal surface using second-order correlation functions.

  16. Superconductivity of metal-induced surface reconstructions on silicon

    NASA Astrophysics Data System (ADS)

    Uchihashi, Takashi

    2016-11-01

    Recent progress in superconducting metal-induced surface reconstructions on silicon is reviewed, mainly focusing on the results of the author’s group. After a brief introduction of an ultrahigh-vacuum (UHV)-low-temperature (LT)-compatible electron transport measurement system, direct observation of the zero resistance state for the Si(111)-(\\sqrt{7} × \\sqrt{3} )-In surface is described, which demonstrates the existence of a superconducting transition in this class of two-dimensional (2D) materials. The measurement and analysis of the temperature dependence of the critical current density indicate that a surface atomic step works as a Josephson junction. This identification is further confirmed by LT-scanning tunneling microscopy (STM) observation of Josephson vortices trapped at atomic steps on the Si(111)-(\\sqrt{7} × \\sqrt{3} )-In surface. These experiments reveal unique features of metal-induced surface reconstructions on silicon that may be utilized to explore novel superconductivity.

  17. Diffusion and surface alloying of gradient nanostructured metals

    PubMed Central

    Lu, Ke

    2017-01-01

    Gradient nanostructures (GNSs) have been optimized in recent years for desired performance. The diffusion behavior in GNS metals is crucial for understanding the diffusion mechanism and relative characteristics of different interfaces that provide fundamental understanding for advancing the traditional surface alloying processes. In this paper, atomic diffusion, reactive diffusion, and surface alloying processes are reviewed for various metals with a preformed GNS surface layer. We emphasize the promoted atomic diffusion and reactive diffusion in the GNS surface layer that are related to a higher interfacial energy state with respect to those in relaxed coarse-grained samples. Accordingly, different surface alloying processes, such as nitriding and chromizing, have been modified significantly, and some diffusion-related properties have been enhanced. Finally, the perspectives on current research in this field are discussed. PMID:28382244

  18. Molecule-to-metal bonds: electrografting polymers on conducting surfaces.

    PubMed

    Palacin, Serge; Bureau, Christophe; Charlier, Julienne; Deniau, Guy; Mouanda, Brigitte; Viel, Pascal

    2004-10-18

    Electrografting is a powerful and versatile technique for modifying and decorating conducting surfaces with organic matter. Mainly based on the electro-induced polymerization of dissolved electro-active monomers on metallic or semiconducting surfaces, it finds applications in various fields including biocompatibility, protection against corrosion, lubrication, soldering, functionalization, adhesion, and template chemistry. Starting from experimental observations, this Review highlights the mechanism of the formation of covalent metal-carbon bonds by electro-induced processes, together with major applications such as derivatization of conducting surfaces with biomolecules that can be used in biosensing, lubrication of low-level electrical contacts, reversible trapping of ionic waste on reactive electrografted surfaces as an alternative to ion-exchange resins, and localized modification of conducting surfaces, a one-step process providing submicrometer grafted areas and which is used in microelectronics.

  19. A Novel Heat Treatment Process for Surface Hardening of Steel: Metal Melt Surface Hardening

    NASA Astrophysics Data System (ADS)

    Fu, Yong-sheng; Zhang, Wei; Xu, Xiaowei; Li, Jiehua; Li, Jun; Xia, Mingxu; Li, Jianguo

    2017-09-01

    A novel heat treatment process for surface hardening of steel has been demonstrated and named as "metal melt surface hardening (MMSH)." A surface layer with a thickness of about 400 μm and a hardness of about 700 HV has been achieved by ejecting AISI 304 stainless steel melt at a temperature of about 1783 K (1510 °C) onto the 40Cr steel surface. This proposed MMSH provides a very promising application for surface hardening of steel.

  20. 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.

  1. Point defect reactions at surfaces and in bulk metals

    NASA Astrophysics Data System (ADS)

    Flynn, C. P.

    2005-02-01

    This paper describes the time evolution of reacting defect assemblies both in bulk metals and on their surfaces. Three areas are treated. The first describes the linear response of reacting assemblies to perturbing fields such as irradiation or temperature change. Alternative long wavelength limits identified here concern: (i) independent diffusion of vacancy- and interstitial-type defects to sinks; and (ii) joint diffusion of defects down a chemical potential gradient, with a separate branch of solutions associated with recombination. The second topic concerns definitions of the chemical potential μ* and temperature T* associated with the defect system itself, as distinct from the properties of the embedding lattice. The utility of these quantities is illustrated by examples including those pertaining to rapid temperature change. μ* and T differ from the lattice values μ,T , to an extent that determines possible energy and particle transfer in such processes as nucleation of new sinks and precipitation from the defect assembly. The role of these quantities in relaxation modes is clarified. Finally, an appendix discusses an approximate model of defect behavior in the bulk, and a speculative discussion of defect behavior on surfaces, both positing homologous properties of the defect systems in metals, when scaled to the melting temperature Tm . These characteristics of a standard metal and a standard close-packed metal surface are employed in the text to identify and contrast typical behaviors of the bulk and surface defect systems of metals. Universal properties that follow from these models are discussed in a second appendix.

  2. Metallic nanostructure formation limited by the surface hydrogen on silicon.

    PubMed

    Perrine, Kathryn A; Teplyakov, Andrew V

    2010-08-03

    Constant miniaturization of electronic devices and interfaces needed to make them functional requires an understanding of the initial stages of metal growth at the molecular level. The use of metal-organic precursors for metal deposition allows for some control of the deposition process, but the ligands of these precursor molecules often pose substantial contamination problems. One of the ways to alleviate the contamination problem with common copper deposition precursors, such as copper(I) (hexafluoroacetylacetonato) vinyltrimethylsilane, Cu(hfac)VTMS, is a gas-phase reduction with molecular hydrogen. Here we present an alternative method to copper film and nanostructure growth using the well-defined silicon surface. Nearly ideal hydrogen termination of silicon single-crystalline substrates achievable by modern surface modification methods provides a limited supply of a reducing agent at the surface during the initial stages of metal deposition. Spectroscopic evidence shows that the Cu(hfac) fragment is present upon room-temperature adsorption and reacts with H-terminated Si(100) and Si(111) surfaces to deposit metallic copper. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) are used to follow the initial stages of copper nucleation and the formation of copper nanoparticles, and X-ray energy dispersive spectroscopy (XEDS) confirms the presence of hfac fragments on the surfaces of nanoparticles. As the surface hydrogen is consumed, copper nanoparticles are formed; however, this growth stops as the accessible hydrogen is reacted away at room temperature. This reaction sets a reference for using other solid substrates that can act as reducing agents in nanoparticle growth and metal deposition.

  3. Chemical Dynamics at Surfaces of Metal Nanomaterials

    DTIC Science & Technology

    2014-07-23

    and to use the new tools to investigate whether a fundamental physical principle, the Born-Oppenheimer Approximation ( BOA ), is valid on the surfaces...systems largely depend on whether BOA is valid12-14. In the following, the accomplishments will be briefly described. 2.1 The vibrational cross angle...nct vibrati ite boxes in (marked w with a simil oretical calc f 4nm Au p rface of 4n angstrom m ation ( BOA d to be much BOA is wh vibrationa very

  4. Plasmonic properties of metal nanoislands: surface integral equations approach

    NASA Astrophysics Data System (ADS)

    Scherbak, S. A.; Lipovskii, A. A.

    2016-08-01

    The surface integral equations method is used to analyse the surface plasmon resonance position in a metal island film formed by non-interacting axisymmetrical prolate/oblate hemispheroids placed on a dielectric substrate. The approach is verified via the comparison of results obtained for a hemisphere on a substrate with the ones obtained using the multipole expansion method. The preference of the integral equations method is in obtaining a simple final analytical expression for a particle polarizability in which any dielectric function of a metal can be substituted. Such simple formulae for the hemispherical particle on the substrate and calculated dependences of the hemispheroid resonant wavelength on its aspect ratio are presented.

  5. Geometrically induced surface polaritons in planar nanostructured metallic cavities

    SciTech Connect

    Davids, P. S.; Intravia, F; Dalvit, Diego A.

    2014-01-14

    We examine the modal structure and dispersion of periodically nanostructured planar metallic cavities within the scattering matrix formulation. By nanostructuring a metallic grating in a planar cavity, artificial surface excitations or spoof plasmon modes are induced with dispersion determined by the periodicity and geometric characteristics of the grating. These spoof surface plasmon modes are shown to give rise to new cavity polaritonic modes at short mirror separations that modify the density of modes in nanostructured cavities. The increased modal density of states form cavity polarirons have a large impact on the fluctuation induced electromagnetic forces and enhanced hear transfer at short separations.

  6. Bacterial adhesion to glass and metal-oxide surfaces.

    PubMed

    Li, Baikun; Logan, Bruce E

    2004-07-15

    Metal oxides can increase the adhesion of negatively-charged bacteria to surfaces primarily due to their positive charge. However, the hydrophobicity of a metal-oxide surface can also increase adhesion of bacteria. In order to understand the relative contribution of charge and hydrophobicity to bacterial adhesion, we measured the adhesion of 8 strains of bacteria, under conditions of low and high-ionic strength (1 and 100 mM, respectively) to 11 different surfaces and examined adhesion as a function of charge, hydrophobicity (water contact angle) and surface energy. Inorganic surfaces included three uncoated glass surfaces and eight metal-oxide thin films prepared on the upper (non-tin-exposed) side of float glass by chemical vapor deposition. The Gram-negative bacteria differed in lengths of lipopolysaccharides on their outer surface (three Escherichia coli strains), the amounts of exopolysaccharides (two Pseudomonas aeruginosa strains), and their known relative adhesion to sand grains (two Burkholderia cepacia strains). One Gram positive bacterium was also used that had a lower adhesion to glass than these other bacteria (Bacillus subtilis). For all eight bacteria, there was a consistent increase in adhesion between with the type of inorganic surface in the order: float glass exposed to tin (coded here as Si-Sn), glass microscope slide (Si-m), uncoated air-side float glass surface (Si-a), followed by thin films of (Co(1-y-z)Fe(y)Cr(z))3O4, Ti/Fe/O, TiO2, SnO2, SnO2:F, SnO2:Sb, A1(2)O3, and Fe2O3 (the colon indicates metal doping, a slash indicates that the metal is a major component, while the dash is used to distinguish surfaces). Increasing the ionic strength from 1 to 100 mM increased adhesion by a factor of 2.0 +/- 0.6 (73% of the sample results were within the 95% CI) showing electrostatic charge was important in adhesion. However, adhesion was not significantly correlated with bacterial charge and contact angle. Adhesion (A) of the eight strains was

  7. Evaluation of Metal-Fueled Surface Reactor Concepts

    SciTech Connect

    Poston, David I.; Marcille, Thomas F.; Kapernick, Richard J.; Hiatt, Matthew T.; Amiri, Benjamin W.

    2007-01-30

    Surface fission power systems for use on the Moon and Mars may provide the first use of near-term reactor technology in space. Most near-term surface reactor concepts specify reactor temperatures <1000 K to allow the use of established material and power conversion technology and minimize the impact of the in-situ environment. Metal alloy fuels (e.g. U-10Zr and U-10Mo) have not traditionally been considered for space reactors because of high-temperature requirements, but they might be an attractive option for these lower temperature surface power missions. In addition to temperature limitations, metal fuels are also known to swell significantly at rather low fuel burnups ({approx}1 a/o), but near-term surface missions can mitigate this concern as well, because power and lifetime requirements generally keep fuel burnups <1 a/o. If temperature and swelling issues are not a concern, then a surface reactor concept may be able to benefit from the high uranium density and relative ease of manufacture of metal fuels. This paper investigates two reactor concepts that utilize metal fuels. It is found that these concepts compare very well to concepts that utilize other fuels (UN, UO2, UZrH) on a mass basis, while also providing the potential to simplify material safeguards issues.

  8. Formation, Removal, and Reformation of Surface Coatings on Various Metal Oxide Surfaces Inspired by Mussel Adhesives.

    PubMed

    Kang, Taegon; Oh, Dongyeop X; Heo, Jinhwa; Lee, Han-Koo; Choy, Seunghwan; Hawker, Craig J; Hwang, Dong Soo

    2015-11-11

    Mussels survive by strongly attaching to a variety of different surfaces, primarily subsurface rocks composed of metal oxides, through the formation of coordinative interactions driven by protein-based catechol repeating units contained within their adhesive secretions. From a chemistry perspective, catechols are known to form strong and reversible complexes with metal ions or metal oxides, with the binding affinity being dependent on the nature of the metal ion. As a result, catechol binding with metal oxides is reversible and can be broken in the presence of a free metal ion with a higher stability constant. It is proposed to exploit this competitive exchange in the design of a new strategy for the formation, removal, and reformation of surface coatings and self-assembled monolayers (SAM) based on catechols as the adhesive unit. In this study, catechol-functionalized tri(ethylene oxide) (TEO) was synthesized as a removable and recoverable self-assembled monolayer (SAM) for use on oxides surfaces. Attachment and detachment of these catechol derivatives on a variety of surfaces was shown to be reversible and controllable by exploiting the high stability constant of catechol to soluble metal ions, such as Fe(III). This tunable assembly based on catechol binding to metal oxides represents a new concept for reformable coatings with applications in fields ranging from friction/wettability control to biomolecular sensing and antifouling.

  9. Cohesion and coordination effects on transition metal surface energies

    NASA Astrophysics Data System (ADS)

    Ruvireta, Judit; Vega, Lorena; Viñes, Francesc

    2017-10-01

    Here we explore the accuracy of Stefan equation and broken-bond model semiempirical approaches to obtain surface energies on transition metals. Cohesive factors are accounted for either via the vaporization enthalpies, as proposed in Stefan equation, or via cohesive energies, as employed in the broken-bond model. Coordination effects are considered including the saturation degree, as suggested in Stefan equation, employing Coordination Numbers (CN), or as the ratio of broken bonds, according to the bond-cutting model, considering as well the square root dependency of the bond strength on CN. Further, generalized coordination numbers CN bar are contemplated as well, exploring a total number of 12 semiempirical formulations on the three most densely packed surfaces of 3d, 4d, and 5d Transition Metals (TMs) displaying face-centered cubic (fcc), body-centered cubic (bcc), or hexagonal close-packed (hcp) crystallographic structures. Estimates are compared to available experimental surface energies obtained extrapolated to zero temperature. Results reveal that Stefan formula cohesive and coordination dependencies are only qualitative suited, but unadvised for quantitative discussion, as surface energies are highly overestimated, favoring in addition the stability of under-coordinated surfaces. Broken-bond cohesion and coordination dependencies are a suited basis for quantitative comparison, where square-root dependencies on CN to account for bond weakening are sensibly worse. An analysis using Wulff shaped averaged surface energies suggests the employment of broken-bond model using CN to gain surface energies for TMs, likely applicable to other metals.

  10. Theoretical Studies of the Surface Tension of Liquid Metal System

    NASA Technical Reports Server (NTRS)

    Stroud, D. G.; Shih, W. H.

    1985-01-01

    A major goal of this project is to understand the surface tension and other thermophysical properties of liquid metals and alloys from a fundamental viewpoint. The approach is to calculate these quantities by a first principles technique which combines the statistical-mechanical theory of the liquid state with an electronic pseudopotential theory of electrons in metals. The inhomogeneity of the surface is treated using an ionic-density-functional formalism developed with the support of NASA. Of particular interest are the variation of surface tension with temperature and impurity concentration: such variations strongly influence the types of convection which make take place in a low-gravity environment. Some progress has already been achieved in computing the reduction of surface tension due to the presence of low-surface-tension impurities, and the corresponding surface segregation of such impurities. In the coming year, it is planned to concentrate on the surface properties of materials of particular interest to the MSA program: Si, Ga and GaSn alloys. An additional goal is to gain some theoretical understanding of the high temperature thermophysical properties of liquid metals, particularly high melting point materials which have not been studied extensively from a theoretical viewpoint.

  11. Theoretical Studies of the Surface Tension of Liquid Metal System

    NASA Technical Reports Server (NTRS)

    Stroud, D. G.; Shih, W. H.

    1985-01-01

    A major goal of this project is to understand the surface tension and other thermophysical properties of liquid metals and alloys from a fundamental viewpoint. The approach is to calculate these quantities by a first principles technique which combines the statistical-mechanical theory of the liquid state with an electronic pseudopotential theory of electrons in metals. The inhomogeneity of the surface is treated using an ionic-density-functional formalism developed with the support of NASA. Of particular interest are the variation of surface tension with temperature and impurity concentration: such variations strongly influence the types of convection which make take place in a low-gravity environment. Some progress has already been achieved in computing the reduction of surface tension due to the presence of low-surface-tension impurities, and the corresponding surface segregation of such impurities. In the coming year, it is planned to concentrate on the surface properties of materials of particular interest to the MSA program: Si, Ga and GaSn alloys. An additional goal is to gain some theoretical understanding of the high temperature thermophysical properties of liquid metals, particularly high melting point materials which have not been studied extensively from a theoretical viewpoint.

  12. Helium atmospheric pressure plasma jets touching dielectric and metal surfaces

    NASA Astrophysics Data System (ADS)

    Norberg, Seth A.; Johnsen, Eric; Kushner, Mark J.

    2015-07-01

    Atmospheric pressure plasma jets (APPJs) are being investigated in the context plasma medicine and biotechnology applications, and surface functionalization. The composition of the surface being treated ranges from plastics, liquids, and biological tissue, to metals. The dielectric constant of these materials ranges from as low as 1.5 for plastics to near 80 for liquids, and essentially infinite for metals. The electrical properties of the surface are not independent variables as the permittivity of the material being treated has an effect on the dynamics of the incident APPJ. In this paper, results are discussed from a computational investigation of the interaction of an APPJ incident onto materials of varying permittivity, and their impact on the discharge dynamics of the plasma jet. The computer model used in this investigation solves Poisson's equation, transport equations for charged and neutral species, the electron energy equation, and the Navier-Stokes equations for the neutral gas flow. The APPJ is sustained in He/O2 = 99.8/0.2 flowing into humid air, and is directed onto dielectric surfaces in contact with ground with dielectric constants ranging from 2 to 80, and a grounded metal surface. Low values of relative permittivity encourage propagation of the electric field into the treated material and formation and propagation of a surface ionization wave. High values of relative permittivity promote the restrike of the ionization wave and the formation of a conduction channel between the plasma discharge and the treated surface. The distribution of space charge surrounding the APPJ is discussed.

  13. Fast Surface Dynamics of Metallic Glass Enable Superlatticelike Nanostructure Growth.

    PubMed

    Chen, L; Cao, C R; Shi, J A; Lu, Z; Sun, Y T; Luo, P; Gu, L; Bai, H Y; Pan, M X; Wang, W H

    2017-01-06

    Contrary to the formation of complicated polycrystals induced by general crystallization, a modulated superlatticelike nanostructure, which grows layer by layer from the surface to the interior of a Pd_{40}Ni_{10}Cu_{30}P_{20} metallic glass, is observed via isothermal annealing below the glass transition temperature. The generation of the modulated nanostructure can be solely controlled by the annealing temperature, and it can be understood based on the fast dynamic and liquidlike behavior of the glass surface. The observations have implications for understanding the glassy surface dynamics and pave a way for the controllable fabrication of a unique and sophisticated nanostructure on a glass surface to realize the properties' modification.

  14. Fast Surface Dynamics of Metallic Glass Enable Superlatticelike Nanostructure Growth

    NASA Astrophysics Data System (ADS)

    Chen, L.; Cao, C. R.; Shi, J. A.; Lu, Z.; Sun, Y. T.; Luo, P.; Gu, L.; Bai, H. Y.; Pan, M. X.; Wang, W. H.

    2017-01-01

    Contrary to the formation of complicated polycrystals induced by general crystallization, a modulated superlatticelike nanostructure, which grows layer by layer from the surface to the interior of a Pd40Ni10Cu30P20 metallic glass, is observed via isothermal annealing below the glass transition temperature. The generation of the modulated nanostructure can be solely controlled by the annealing temperature, and it can be understood based on the fast dynamic and liquidlike behavior of the glass surface. The observations have implications for understanding the glassy surface dynamics and pave a way for the controllable fabrication of a unique and sophisticated nanostructure on a glass surface to realize the properties' modification.

  15. Visual Inspection of Machined Metallic High-Precision Surfaces

    NASA Astrophysics Data System (ADS)

    Pernkopf, Franz; O'Leary, Paul

    2002-12-01

    This paper presents a surface inspection prototype of an automatic system for precision ground metallic surfaces, in this case bearing rolls. The surface reflectance properties are modeled and verified with optical experiments. The aim being to determine the optical arrangement for illumination and observation, where the contrast between errors and intact surface is maximized. A new adaptive threshold selection algorithm for segmentation is presented. Additionally, is included an evaluation of a large number of published sequential search algorithms for selection of the best subset of features for the classification with a comparison of their computational requirements. Finally, the results of classification for 540 flaw images are presented.

  16. Laser surface treatment of amorphous metals

    NASA Astrophysics Data System (ADS)

    Katakam, Shravana K.

    Amorphous materials are used as soft magnetic materials and also as surface coatings to improve the surface properties. Furthermore, the nanocrystalline materials derived from their amorphous precursors show superior soft magnetic properties than amorphous counter parts for transformer core applications. In the present work, laser based processing of amorphous materials will be presented. Conventionally, the nanocrystalline materials are synthesized by furnace heat treatment of amorphous precursors. Fe-based amorphous/nanocrystalline materials due to their low cost and superior magnetic properties are the most widely used soft magnetic materials. However, achieving nanocrystalline microstructure in Fe-Si-B ternary system becomes very difficult owing its rapid growth rate at higher temperatures and sluggish diffusion at low temperature annealing. Hence, nanocrystallization in this system is achieved by using alloying additions (Cu and Nb) in the ternary Fe-Si-B system. Thus, increasing the cost and also resulting in reduction of saturation magnetization. laser processing technique is used to achieve extremely fine nanocrystalline microstructure in Fe-Si-B amorphous precursor. Microstructure-magnetic Property-laser processing co-relationship has been established for Fe-Si-B ternary system using analytical techniques. Laser processing improved the magnetic properties with significant increase in saturation magnetization and near zero coercivity values. Amorphous materials exhibit excellent corrosion resistance by virtue of their atomic structure. Fe-based amorphous materials are economical and due to their ease of processing are of potential interest to synthesize as coatings materials for wear and corrosion resistance applications. Fe-Cr-Mo-Y-C-B amorphous system was used to develop thick coatings on 4130 Steel substrate and the corrosion resistance of the amorphous coatings was improved. It is also shown that the mode of corrosion depends on the laser processing

  17. Surface Characterization of Retrieved Metal-on-Metal Total Hip Implants from Patients with Adverse Reaction to Metal Debris

    PubMed Central

    Burbano, Maria; Russell, Robert; Huo, Michael; Welch, Robert; Roy, Diana; Rodrigues, Danieli C.

    2014-01-01

    The use of metal-on-metal (MoM) total hip implants has decreased recently due to reports of high failure rates and adverse local tissue reaction (ALTR). It has been hypothesized that wear metal debris released from CoCr bearing surfaces may provoke delayed hypersensitivity reactions. The goal of this study is to evaluate the microscopic bearing surface characteristics of implants revised due to evidence of ALTR. The bearing surface of each head and cup was analyzed using multiple microscopy techniques for characterization of the surface features. The presence of severe mechanical scratching was a common characteristic found in all of the implants evaluated. Mechanical factors seemed to be the prevalent failure mode related to the appearance of ALTR with this particular set of retrieved implants. PMID:28788544

  18. Modelling of Surfaces. Part 1: Monatomic Metallic Surfaces Using Equivalent Crystal Theory

    NASA Technical Reports Server (NTRS)

    Bozzolo, Guillermo; Ferrante, John; Rodriguez, Agustin M.

    1994-01-01

    We present a detailed description of equivalent crystal theory focusing on its application to the study of surface structure. While the emphasis is in the structure of the algorithm and its computational aspects, we also present a comprehensive discussion on the calculation of surface energies of metallic systems with equivalent crystal theory and other approaches. Our results are compared to experiment and other semiempirical as well as first-principles calculations for a variety of fcc and bcc metals.

  19. A general strategy for the ultrafast surface modification of metals

    NASA Astrophysics Data System (ADS)

    Shen, Mingli; Zhu, Shenglong; Wang, Fuhui

    2016-12-01

    Surface modification is an essential step in engineering materials that can withstand the increasingly aggressive environments encountered in various modern energy-conversion systems and chemical processing industries. However, most traditional technologies exhibit disadvantages such as slow diffusion kinetics, processing difficulties or compatibility issues. Here, we present a general strategy for the ultrafast surface modification of metals inspired by electromigration, using aluminizing austenitic stainless steel as an example. Our strategy facilitates the rapid formation of a favourable ductile surface layer composed of FeCrAl or β-FeAl within only 10 min compared with several hours in conventional processes. This result indicates that electromigration can be used to achieve the ultrafast surface modification of metals and can overcome the limitations of traditional technologies. This strategy could be used to aluminize ultra-supercritical steam tubing to withstand aggressive oxidizing environments.

  20. A general strategy for the ultrafast surface modification of metals

    PubMed Central

    Shen, Mingli; Zhu, Shenglong; Wang, Fuhui

    2016-01-01

    Surface modification is an essential step in engineering materials that can withstand the increasingly aggressive environments encountered in various modern energy-conversion systems and chemical processing industries. However, most traditional technologies exhibit disadvantages such as slow diffusion kinetics, processing difficulties or compatibility issues. Here, we present a general strategy for the ultrafast surface modification of metals inspired by electromigration, using aluminizing austenitic stainless steel as an example. Our strategy facilitates the rapid formation of a favourable ductile surface layer composed of FeCrAl or β-FeAl within only 10 min compared with several hours in conventional processes. This result indicates that electromigration can be used to achieve the ultrafast surface modification of metals and can overcome the limitations of traditional technologies. This strategy could be used to aluminize ultra-supercritical steam tubing to withstand aggressive oxidizing environments. PMID:27924909

  1. Thin water film formation on metal oxide crystal surfaces.

    PubMed

    Gilbert, Benjamin; Katz, Jordan E; Rude, Bruce; Glover, T E; Hertlein, Marcus P; Kurz, Charles; Zhang, Xiaoyi

    2012-10-09

    Reactions taking place at hydrated metal oxide surfaces are of considerable environmental and technological importance. Surface-sensitive X-ray methods can provide structural and chemical information on stable interfacial species, but it is challenging to perform in situ studies of reaction kinetics in the presence of water. We have implemented a new approach to creating a micrometer-scale water film on a metal oxide surface by combining liquid and gas jets on a spinning crystal. The water films are stable indefinitely and sufficiently thin to allow grazing incidence X-ray reflectivity and spectroscopy measurements. The approach will enable studies of a wide range of surface reactions and is compatible with interfacial optical-pump/X-ray-probe studies.

  2. A general strategy for the ultrafast surface modification of metals.

    PubMed

    Shen, Mingli; Zhu, Shenglong; Wang, Fuhui

    2016-12-07

    Surface modification is an essential step in engineering materials that can withstand the increasingly aggressive environments encountered in various modern energy-conversion systems and chemical processing industries. However, most traditional technologies exhibit disadvantages such as slow diffusion kinetics, processing difficulties or compatibility issues. Here, we present a general strategy for the ultrafast surface modification of metals inspired by electromigration, using aluminizing austenitic stainless steel as an example. Our strategy facilitates the rapid formation of a favourable ductile surface layer composed of FeCrAl or β-FeAl within only 10 min compared with several hours in conventional processes. This result indicates that electromigration can be used to achieve the ultrafast surface modification of metals and can overcome the limitations of traditional technologies. This strategy could be used to aluminize ultra-supercritical steam tubing to withstand aggressive oxidizing environments.

  3. Phisicochemistry of alkaline-earth metals oxides surface

    NASA Astrophysics Data System (ADS)

    Ekimova, Irina; Minakova, Tamara; Ogneva, Tatyana

    2016-01-01

    The surface state of alkaline-earth metals and magnesium oxides obtained by means of commercial and laboratory ways has been studied in this paper. A complex of methods has been used for identification, determination of a phase composition and morphology of the samples. The high basic character of surface centres has been shown with the help of pH-metry and adsorption of indicators methods. Acid-basic parameters (pHt, pHiis, etc.) can be used for the estimation of a general acid-basic state of metal oxides samples surface and for the supposition about different nature and strength of acid-basic centres as well as for the initial control in the process of acid basic properties of solid oxides surface properties evaluation.

  4. Effective mineral coatings for hardening the surface of metallic materials

    NASA Astrophysics Data System (ADS)

    Kislov, S. V.; Kislov, V. G.; Skazochkin, A. V.; Bondarenko, G. G.; Tikhonov, A. N.

    2015-07-01

    The structural changes that occur in the surface and surface layers of steel 20Kh13 and titanium alloy PT-3V (Russian designation) samples after each stage of hardening due to a formed mineral surface layer are studied by optical microscopy, transmission electron microscopy, and scanning electron microscopy. Electric spark alloying, pressing, and ultrasonic processing are used to reach the effect of volume compression of the base metal and the mineral in the plastic deformation zone. As a result, applied mineral particles concentrate in preliminarily created microvoids in a thin surface layer. The surface layer thus modified acquires a high hardness and wear resistance. Durometry shows that the hardness of the processed sample surfaces increases more than twofold. Therefore, the developed technology of creating a mineral coating can be used to increase the tribological properties of the surfaces of the parts, units, and mechanisms of turbine, pump, and mining equipment, which undergo intense wear during operation.

  5. Laser Cleaning of Metal Surface — Laboratory Investigations

    NASA Astrophysics Data System (ADS)

    Mottner, P.; Wiedemann, G.; Haber, G.; Conrad, W.; Gervais, A.

    The interaction of various metal alloys with laser energy generated by a Nd:YAG medium (λ=1064 nm, 532 nm, and 355 nm) has been examined systematically by the variation of laser parameters. With the help of model coupons, alteration/ablation thresholds of uncorroded/corroded surfaces of iron, pure copper and copper alloys were determined, leading to first recommendations for the cleaning of originals. Surface absorption measurements in the UV/VIS/IR wavelength regions completed the interaction studies.

  6. Correlation between surface tension and critical temperatures of liquid metals.

    PubMed

    Blairs, Sidney; Abbasi, Mohammad Hassan

    2006-12-15

    The inter-relationship of surface tension sigma, molar volume V, and critical temperature Tc has been examined using experimental values for eighteen liquid metals. Hard-sphere diameters a correlate with the equation a(5/2) = 8.9733 x 10(-19) V (sigma/Tc)(1/4) - 1.0459 x 10(-25). Unknown Tc may be estimated using surface tension and liquid density values.

  7. Quantum Chemistry for Surface Segregation in Metal Alloys

    SciTech Connect

    Sholl, David

    2006-08-31

    Metal alloys are vital materials for the fabrication of high-flux, high-selectivity hydrogen separation membranes. A phenomenon that occurs in alloys that does not arise in pure metals is surface segregation, where the composition of the surface differs from the bulk composition. Little is known about the strength of surface segregation in the alloys usually considered for hydrogen membranes. Despite this lack of knowledge, surface segregation may play a decisive role in the ability of appropriately chosen alloys to be resistant to chemical poisoning, since membrane poisoning is controlled by surface chemistry. The aim of this Phase I project is to develop quantum chemistry approaches to assess surface segregation in a prototypical hydrogen membrane alloy, fcc Pd{sub 75}Cu{sub 25}. This alloy is known experimentally to have favorable surface properties as a poison resistant H{sub 2} purification membrane (Kamakoti et al., Science 307 (2005) 569-573), but previous efforts at modeling surfaces of this alloy have ignored the possible role of surface segregation (Alfonso et al., Surf. Sci. 546 (2003) 12-26).

  8. Metal-on-metal surface replacement: a triumph of hope over reason: opposes.

    PubMed

    Su, Edwin P; Su, Sherwin L

    2011-09-09

    Hip resurfacing has been performed for over a decade but still raises controversy as an alternative to traditional total hip arthroplasty (THA). Concerns exist about the potential complications of hip resurfacing, including femoral neck fracture and osteonecrosis of the femoral head. Recently, attention has been given to the metal-on-metal bearing of hip resurfacing with regard to production of metal ions, possible tissue necrosis, and rare instances of metal hypersensitivity. Given the success of the gold-standard THA, it is understandable why some surgeons believe metal-on-metal surface replacement to be "a triumph of hope over reason." However, this article opposes that viewpoint, demonstrating that data exist to justify the practice of preserving bone in younger patients. Hip resurfacing can maintain femoral bone without the expense of removing additional acetabular bone by using modern implants with incremental sizing. Furthermore, many of the problems cited with the bearing couple (such as excess metal production) have been due to poor implant designs, which have now been removed from the market. Finally, we now realize that the metal-on-metal articulation is more sensitive to malposition; thus, good surgical technique and experience can solve many of the problems that have been cited in the past. National registry results confirm that in a select population, hip resurfacing performs comparably to THA, while fulfilling the goal of bone preservation.

  9. Temporal pulse shaping for smoothing of printed metal surfaces

    NASA Astrophysics Data System (ADS)

    Berg, Yuval; Zenou, Michael; Dolev, Omer; Kotler, Zvi

    2015-01-01

    The surfaces of laser-induced forward transfer (LIFT) printed metal structures show typical roughness characteristic of the metal droplet size (3 to 10 μm). Submicron voids are often observed in the bulk of such printed metal structures with consequences on the mechanical strength, chemical resistivity, and electrical conductivity. We present the results of our efforts to reduce surface roughness and bulk voids by controlled laser melting. We have used temporally shaped pulses from a fiber laser tunable in the range from 1 to 600 ns in order to improve the quality of LIFT printed copper and aluminum structures. For the best case shown, roughness was improved from RRMS=0.8 μm to RRMS=0.2 μm and the relative percentage of the voids was reduced from 7.3% to 0.9%.

  10. Immobilization of Metal Nanoparticles in Surface Layer of Silica Matrices

    NASA Astrophysics Data System (ADS)

    Katok, Kseniia; Tertykh, Valentin; Yanishpolskii, Victor

    Gold and silver nanoparticles were obtained by in situ reduction with silicon hydride groups grafted to the mesoporous MCM-41 silica surface. Nickel-, cobalt-, and iron-containing silicas were synthesized by chemisorption of appropriate metal acetylacetonates with following reduction in the acetylene atmosphere. Such metal-containing MCM-41 matrices have been applied for preparation of carbon nanostructures at pyrolytic decomposition of acetylene. From transmission electron microscopy (TEM) data a lot of carbon nanotubes were formed, namely tubes with external diameter of 10-35 nm for Ni-, 42-84 nm for Co-, and 14-24 nm for Fecontaining silicas. In the metal absence on the silica surface low yield of nanotubes (up to 2%) was detected.

  11. Metal halide solid-state surface treatment for nanocrystal materials

    DOEpatents

    Luther, Joseph M.; Crisp, Ryan; Beard, Matthew C.

    2016-04-26

    Methods of treating nanocrystal and/or quantum dot devices are described. The methods include contacting the nanocrystals and/or quantum dots with a solution including metal ions and halogen ions, such that the solution displaces native ligands present on the surface of the nanocrystals and/or quantum dots via ligand exchange.

  12. Heat transfer in free-surface, flowing liquid metal

    NASA Astrophysics Data System (ADS)

    Rhoads, J.; Spence, E.; Edlund, E.; Sloboda, P.; Ji, H.

    2012-10-01

    The presence of a strong external magnetic field affects structures within the flow of conducting fluids such as liquid metals, which may have significant implications for thermal convection in proposed liquid-metal divertor concepts. Experiments have been conducted in the Liquid Metal Experiment (LMX) using a GaInSn eutectic alloy as a working fluid to investigate the anisotropization due to the magnetic field on turbulent structures in the flow and the resulting effects on convective heat transfer. These experiments considered free-surface, wide aspect-ratio flow through a channel situated in a magnetic field (up to Ha 50). Heat was injected into the fluid via resistive heaters located either on the surface or submerged in the fluid. The thermal profile was tracked on the surface of the flow by a mid-wavelength IR camera and at the bottom of the flow by a dense array of fine gage thermocouples. Along with internal velocity measurements, the temporal and spatial thermal profiles show the effects of the magnetic field on convection, yielding valuable insight into the behavior of heat transfer in free-surface, liquid metal flows. Experimental results and proposed explanations will be presented.

  13. PARTITION COEFFICIENTS FOR METALS IN SURFACE WATER, SOIL, AND WASTE

    EPA Science Inventory

    This report presents metal partition coefficients for the surface water pathway and for the source model used in the Multimedia, Multi-pathway, Multi-receptor Exposure and Risk Assessment (3MRA) technology under development by the U.S. Environmental Protection Agency. Partition ...

  14. Overlap Integrals for Atom-Metal Surface Interactions.

    DTIC Science & Technology

    1985-05-01

    of using the numerical wavefunctions from this model, we shall consider the metal electrons as particle - in - a - box . Such ’ wavefunctions are good...electronic wavevector parallel to the surface. f(z) is the one-dimensional particle - in - a - box wavefunction: 21/2.𔃼 f(z) = () sin(kz* e ) (9a)z k for -L < z

  15. PARTITION COEFFICIENTS FOR METALS IN SURFACE WATER, SOIL, AND WASTE

    EPA Science Inventory

    This report presents metal partition coefficients for the surface water pathway and for the source model used in the Multimedia, Multi-pathway, Multi-receptor Exposure and Risk Assessment (3MRA) technology under development by the U.S. Environmental Protection Agency. Partition ...

  16. Surface Charge Development on Transition Metal Sulfides: An Electrokinetic Study

    NASA Astrophysics Data System (ADS)

    Bebie, Joakim; Schoonen, Martin A. A.; Fuhrmann, Mark; Strongin, Daniel R.

    1998-02-01

    The isoelectric points, pH i.e.p., of ZnS, PbS, CuFeS 2, FeS, FeS 2, NiS 2, CoS 2, and MnS 2 in NaCl supported electrolyte solutions are estimated to be between pH 3.3 and 0.6, with most of the isoelectric points below pH 2. The first electrokinetic measurements on NiS 2, CoS 2, and MnS 2 are reported here. Below pH i.e.p. the metal-sulfide surfaces are positively charged, above pH i.e.p. the surfaces are negatively charged. The addition of Me 2+ ions shifts the pH i.e.p. and changes the pH dependence considerably. The isoelectric points of the measured transition metal sulfides in the absence of metal ions or dissolved sulfide (H 2S or HS -) are in agreement with those found in earlier studies. The pH range of observed isoelectric points for metal sulfides (0.6-3.3) is compared to the considerably wider pH i.e.p. range (2-12) found for oxides. The correlation between pH i.e.p. and the electronegativities of the metal sulfides suggests that all metal sulfides will have an isoelectric point between pH 0.6 and 3.3. Compared to metal oxides, sulfides exhibit an isoelectric point that is largely independent of the nature of the metal cation in the solid.

  17. Enhanced Raman spectroscopic study of rotational isomers on metal surfaces

    NASA Technical Reports Server (NTRS)

    Loo, B. H.; Lee, Y. G.; Frazier, D. O.

    1986-01-01

    Surfaced-enhanced Raman spectroscopy has been used to study rotational isomers of succinonitrile and N-methyl-thioacetamide on Cu and Ag surfaces. Both the gauche and trans conformers of succinonitrile are found to chemisorb on the metal surface. The doubly degenerate nu(C-triple bond-N) in the free molecules is removed when succinonitrile adsorbs on copper, which indicates that the two (C-triple bond-N) groups are no longer chemically equivalent. Both conformers are found to coordinate to the copper surface through the pi system of one of the two (C-triple bond-N) groups. In the case of N-methyl-thioacetamide, the population of the cis isomer is greatly increased on Cu and Ag surfaces. This is probably due to surface-induced cis-trans isomerization, in which the predominant trans isomer is converted to the cis isomer.

  18. Microbial Specificity of Metallic Surfaces Exposed to Ambient Seawater

    PubMed Central

    Zaidi, B. R.; Bard, R. F.; Tosteson, T. R.

    1984-01-01

    High-molecular-weight materials associated with the extracellular matrix and film found on titanium and aluminum surfaces after exposure to flowing coastal seawater were isolated. This material was purified by hydroxylapatite chromatography and subsequently employed to produce antibodies in the toad, Bufo marinus. The antibodies were immobilized on a solid support and employed to isolate adhesion-enhancing, high-molecular-weight materials from the laboratory culture media of bacterial strains recovered from the respective metallic surfaces during the course of their exposure to seawater. The adhesion-enhancing materials produced by the surface-associated bacterial strains were immunologically related to the extracellular biofouling matrix material found on the surfaces from which these bacteria were isolated. The surface selectivity of these bacterial strains appeared to be based on the specificity of the interaction between adhesion-enhancing macromolecules produced by these bacteria and the surfaces in question. PMID:16346622

  19. Microbial specificity of metallic surfaces exposed to ambient seawater

    SciTech Connect

    Zaidi, B.R.; Bard, R.F.; Tosteson, T.R.

    1984-09-01

    High-molecular-weight materials associated with the extracellular matrix and film found on titanium and aluminum surfaces after exposure to flowing coastal seawater were isolated. This material was purified by hydroxylapatite chromatography and subsequently employed to produce antibodies in the toad, Bufo marinus. The antibodies were immobilized on a solid support and employed to isolate adhesion-enhancing, high-molecular-weight materials from the laboratory culture media of bacterial strains recovered from the respective metallic surfaces during the course of their exposure to seawater. The adhesion-enhancing materials produced by the surface-associated bacterial strains were immunologically related to the extracellular biofouling matrix material found on the surfaces from which these bacteria were isolated. The surface selectivity of these bacterial strains appeared to be based on the specificity of the interaction between adhesion-enhancing macromolecules produced by these bacteria and the surfaces in question. 30 references, 6 tables.

  20. CO2 hydrogenation on a metal hydride surface.

    PubMed

    Kato, Shunsuke; Borgschulte, Andreas; Ferri, Davide; Bielmann, Michael; Crivello, Jean-Claude; Wiedenmann, Daniel; Parlinska-Wojtan, Magdalena; Rossbach, Peggy; Lu, Ye; Remhof, Arndt; Züttel, Andreas

    2012-04-28

    The catalytic hydrogenation of CO(2) at the surface of a metal hydride and the corresponding surface segregation were investigated. The surface processes on Mg(2)NiH(4) were analyzed by in situ X-ray photoelectron spectroscopy (XPS) combined with thermal desorption spectroscopy (TDS) and mass spectrometry (MS), and time-of-flight secondary ion mass spectrometry (ToF-SIMS). CO(2) hydrogenation on the hydride surface during hydrogen desorption was analyzed by catalytic activity measurement with a flow reactor, a gas chromatograph (GC) and MS. We conclude that for the CO(2) methanation reaction, the dissociation of H(2) molecules at the surface is not the rate controlling step but the dissociative adsorption of CO(2) molecules on the hydride surface.

  1. Photodissociation near a rough metal surface: Effect of reaction fields

    NASA Astrophysics Data System (ADS)

    Das, Purna C.; Puri, Ashok; George, Thomas F.

    1990-12-01

    The modification of the photochemical dissociation rate of molecules in the presence of a rough metal surface is explored. Classical electromagnetic calculations are presented for the photodissociation rate of a point dipole near a rough surface modeled as a hemispheroidal bump on a semi-infinite flat plane. A correction is introduced by accounting for the reaction fields due to the dipole-substrate system radiating photons and coupling to delocalized surface plasmons. The effects of the shape and size of the bump, and the separation of the molecule from the bump on the rate of photodissociation of the molecule, are studied numerically.

  2. The surface chemistry of metal-organic frameworks.

    PubMed

    McGuire, Christina V; Forgan, Ross S

    2015-03-28

    Metal-organic frameworks (MOFs) have received particular attention over the last 20 years as a result of their attractive properties offering potential applications in a number of areas. Typically, these characteristics are tuned by functionalisation of the bulk of the MOF material itself. This Feature Article focuses instead on modification of MOF particles at their surfaces only, which can also offer control over the bulk properties of the material. The differing surface modification techniques available to the synthetic chemist will be discussed, with a focus on the effect of surface modification of MOFs on their fundamental properties and application in adsorption, catalysis, drug delivery and other areas.

  3. Effects of GlidArc plasma treatment on metallic surface

    NASA Astrophysics Data System (ADS)

    Astanei, D.; Ursache, M.; Hnatiuc, E.; Stoica, I.; Hnatiuc, B.; Felea, C.

    2016-12-01

    This paper presents the GlidArc plasma effects on some metallic surfaces often used in dentistry: zirconium, titanium and nickel - chromium alloy plates. For the experiments performed, a GlidArc reactor with two planar electrodes has been used. During the tests, the gas flow has been kept constant while the treatment time and the distance between the plasma and the sample were modified. The surfaces were analyzed using atomic force microscopy (AFM) in order to determine the surface morphological modifications induced by the plasma treatment.

  4. Enhanced electron?phonon coupling at metal surfaces

    NASA Astrophysics Data System (ADS)

    Plummer, E. W.; Shi, Junren; Tang, S.-J.; Rotenberg, Eli; Kevan, S. D.

    2003-12-01

    Recent advances in experimental techniques and theoretical capabilities associated with the study of surfaces show promise for producing in unprecedented detail a picture of electron-phonon coupling. These investigations on surfaces of relatively simple metals can be the platform for understanding functionality in complex materials associated with the coupling between charge and the lattice. In this article, we present an introduction to electron-phonon coupling, especially in systems with reduced dimensionality, and the recent experimental and theoretical achievements. Then, we try to anticipate the exciting future created by advances in surface physics.

  5. Polymer surface treatment for improvement of metal-polymer adhesion

    NASA Astrophysics Data System (ADS)

    Neagu, E.; Neagu, R.

    1993-03-01

    The interaction between a low-pressure gas plasma and organic materials has mechanical (surface cleaning and dry micro-etching) and electrostatic (cross-linking and surface activation) effects. Corrosion of a fluorinated ethylenepropylene (FEP) sample was studied for different conditions. The corrosion rate of FEP depends on the gas and on the gas pressure and has the highest value for oxygen. The modifications of the sample surface were studied by contact-angle measurements for water and formamide and by the thermally stimulated discharge current method. The optimum parameters for a continuum vacuum metallization process of FEP are presented.

  6. Generation of singlet oxygen on the surface of metal oxides

    NASA Astrophysics Data System (ADS)

    Kiselev, V. M.; Kislyakov, I. M.; Burchinov, A. N.

    2016-04-01

    Generation of singlet oxygen on the surface of metal oxides is studied. It is shown that, under conditions of heterogeneous photo-catalysis, along with the conventional mechanism of singlet oxygen formation due to the formation of electron-hole pairs in the oxide structure, there is an additional and more efficient mechanism involving direct optical excitation of molecular oxygen adsorbed on the oxide surface. The excited adsorbate molecule then interacts with the surface or with other adsorbate molecules. It is shown that, with respect to singlet oxygen generation, yttrium oxide is more than an order of magnitude more efficient than other oxides, including titanium dioxide.

  7. Strong Casimir force reduction through metallic surface nanostructuring

    PubMed Central

    Intravaia, Francesco; Koev, Stephan; Jung, Il Woong; Talin, A. Alec; Davids, Paul S.; Decca, Ricardo S.; Aksyuk, Vladimir A.; Dalvit, Diego A. R.; López, Daniel

    2013-01-01

    The Casimir force between bodies in vacuum can be understood as arising from their interaction with an infinite number of fluctuating electromagnetic quantum vacuum modes, resulting in a complex dependence on the shape and material of the interacting objects. Becoming dominant at small separations, the force has a significant role in nanomechanics and object manipulation at the nanoscale, leading to a considerable interest in identifying structures where the Casimir interaction behaves significantly different from the well-known attractive force between parallel plates. Here we experimentally demonstrate that by nanostructuring one of the interacting metal surfaces at scales below the plasma wavelength, an unexpected regime in the Casimir force can be observed. Replacing a flat surface with a deep metallic lamellar grating with sub-100 nm features strongly suppresses the Casimir force and for large inter-surfaces separations reduces it beyond what would be expected by any existing theoretical prediction. PMID:24071657

  8. Laser Nanostructurization of the Metal and Alloy Surfaces

    NASA Astrophysics Data System (ADS)

    Kanavin, Andrei; Kozlovskaya, Natalia; Krokhin, Oleg; Zavestovskaya, Irina

    2010-10-01

    The results from experimental and theoretical investigation of material pulsed laser treatment aimed at obtaining nano- and microstructured surface are presented. An experiment has been performed on the modification of indium surface using a solid-state diode-pumped laser. It has been shown that nano- and micro-size structures are formed under laser melting and fast crystallization of the metal surface. The kinetics of the crystallization of metals under superfast cooling. The distribution function for crystalline nuclei dimensions is analytically found within the framework of the classical kinetic equation in case of superfast temperature changing. The average number of particles in the crystalline nuclei and relative volume of the crystalline phase are determined as functions of thermodynamic and laser treatment regime parameters. Good agreement is observed with experimental results for ultrashort laser pulses induced micro- and nanostructures production.

  9. Fine tuning of graphene-metal adhesion by surface alloying.

    PubMed

    Alfè, D; Pozzo, M; Miniussi, E; Günther, S; Lacovig, P; Lizzit, S; Larciprete, R; Santos Burgos, B; Menteş, T O; Locatelli, A; Baraldi, A

    2013-01-01

    We show that bimetallic surface alloying provides a viable route for governing the interaction between graphene and metal through the selective choice of the elemental composition of the surface alloy. This concept is illustrated by an experimental and theoretical characterization of the properties of graphene on a model PtRu surface alloy on Ru(0001), with a concentration of Pt atoms in the first layer between 0 and 50%. The progressive increase of the Pt content determines the gradual detachment of graphene from the substrate, which results from the modification of the carbon orbital hybridization promoted by Pt. Alloying is also found to affect the morphology of graphene, which is strongly corrugated on bare Ru, but becomes flat at a Pt coverage of 50%. The method here proposed can be readily extended to several supports, thus opening the way to the conformal growth of graphene on metals and to a full tunability of the graphene-substrate interaction.

  10. Surface entropy of liquid transition and noble metals

    NASA Astrophysics Data System (ADS)

    Gosh, R. C.; Das, Ramprosad; Sen, Sumon C.; Bhuiyan, G. M.

    2015-07-01

    Surface entropy of liquid transition and noble metals has been investigated using an expression obtained from the hard-sphere (HS) theory of liquid. The expression is developed from the Mayer's extended surface tension formula [Journal of Non-Crystalline Solids 380 (2013) 42-47]. For interionic interaction in metals, Brettonet-Silbert (BS) pseudopotentials and embedded atom method (EAM) potentials have been used. The liquid structure is described by the variational modified hypernetted chain (VMHNC) theory. The essential ingredient of the expression is the temperature dependent effective HS diameter (or packing fraction), which is calculated from the aforementioned potentials together with the VMHNC theory. The obtained results for the surface entropy using the effective HS diameter are found to be good in agreement with the available experimental as well as other theoretical values.

  11. Strong Casimir force reduction through metallic surface nanostructuring.

    PubMed

    Intravaia, Francesco; Koev, Stephan; Jung, Il Woong; Talin, A Alec; Davids, Paul S; Decca, Ricardo S; Aksyuk, Vladimir A; Dalvit, Diego A R; López, Daniel

    2013-01-01

    The Casimir force between bodies in vacuum can be understood as arising from their interaction with an infinite number of fluctuating electromagnetic quantum vacuum modes, resulting in a complex dependence on the shape and material of the interacting objects. Becoming dominant at small separations, the force has a significant role in nanomechanics and object manipulation at the nanoscale, leading to a considerable interest in identifying structures where the Casimir interaction behaves significantly different from the well-known attractive force between parallel plates. Here we experimentally demonstrate that by nanostructuring one of the interacting metal surfaces at scales below the plasma wavelength, an unexpected regime in the Casimir force can be observed. Replacing a flat surface with a deep metallic lamellar grating with sub-100 nm features strongly suppresses the Casimir force and for large inter-surfaces separations reduces it beyond what would be expected by any existing theoretical prediction.

  12. Recommended values of clean metal surface work functions

    SciTech Connect

    Derry, Gregory N. Kern, Megan E.; Worth, Eli H.

    2015-11-15

    A critical review of the experimental literature for measurements of the work functions of clean metal surfaces of single-crystals is presented. The tables presented include all results found for low-index crystal faces except cases that were known to be contaminated surfaces. These results are used to construct a recommended value of the work function for each surface examined, along with an uncertainty estimate for that value. The uncertainties are based in part on the error distribution for all measured work functions in the literature, which is included here. The metals included in this review are silver (Ag), aluminum (Al), gold (Au), copper (Cu), iron (Fe), iridium (Ir), molybdenum (Mo), niobium (Nb), nickel (Ni), palladium (Pd), platinum (Pt), rhodium (Rh), ruthenium (Ru), tantalum (Ta), and tungsten (W)

  13. Surface cleaning of metal wire by atmospheric pressure plasma

    NASA Astrophysics Data System (ADS)

    Nakamura, T.; Buttapeng, C.; Furuya, S.; Harada, N.

    2009-11-01

    In this study, the possible application of atmospheric pressure dielectric barrier discharge plasma for the annealing of metallic wire is examined and presented. The main purpose of the current study is to examine the surface cleaning effect for a cylindrical object by atmospheric pressure plasma. The experimental setup consists of a gas tank, plasma reactor, and power supply with control panel. The gas assists in the generation of plasma. Copper wire was used as an experimental cylindrical object. This copper wire was irradiated with the plasma, and the cleaning effect was confirmed. The result showed that it is possible to remove the tarnish which exists on the copper wire surface. The experiment reveals that atmospheric pressure plasma is usable for the surface cleaning of metal wire. However, it is necessary to examine the method for preventing oxidization of the copper wire.

  14. Functionalizing the Surface of Lithium-Metal Anodes

    DOE PAGES

    Buonaiuto, Megan; Neuhold, Susanna; Schroeder, David J.; ...

    2014-09-03

    Metal-air batteries are an important aspect of many beyond lithium ion research efforts. However, as our understanding of how molecular oxygen can act as a rechargeable cathode has progressed; the problems associated with how these materials at various states of charge interact with the lithium metal anode are only beginning to come to the surface. In this study we have devised a method to coat the surface a lithium with a functional group to act as either an anchor for further derivation studies or be polymerized to create a nanometer thick polymer coating attached to the surface by silane groups.more » These stable films, formed by polymerization of vinyl substituents, lower cell impedance at the electrode and over the first 50 cycles, increase cycling efficiency and demonstrate lower capacity fade.« less

  15. Fractal properties of aggregates of metal nanoclusters on solid surface

    NASA Astrophysics Data System (ADS)

    Samsonov, V. M.; Kuznetsova, Yu. V.; D'yakova, E. V.

    2016-02-01

    AFM images are used to determine and analyze fractal characteristics (cluster fraction dimension and lacunarity) of aggregates of Au and Ag nanoclusters on metal films of the same metal produced with the aid of thermal vacuum deposition on mica surface. A fractal dimension of 1.6 that corresponds to typical samples with relatively uniform distribution of nanoclusters on the film surface is in agreement with the mean value calculated from experimental data of Belko et al., who studied the fractal dimension of Au nanoclusters on a different dielectric (quartz) surface. When a compact single aggregate of Au nanoclusters is formed on a certain active center or defect, the fractal cluster dimension decreases to 1.4. The experimental data are compared with the results of existing theoretical models of association of nanoclusters in 2D systems.

  16. Kondo Screening and Fermi Surface in the Antiferromagnetic Metal Phase

    NASA Astrophysics Data System (ADS)

    Yamamoto, Seiji; Si, Qimiao

    2006-03-01

    We address the Kondo effect deep inside the antiferromagnetic metal phase of a Kondo lattice Hamiltonian with SU(2) invariance. The local- moment component is described in terms of a non-linear sigma model. The Fermi surface of the conduction electron component is taken to be sufficiently small, so that it is not spanned by the antiferromagnetic wavevector. The effective low energy form of the Kondo coupling simplifies drastically, corresponding to the uniform component of the magnetization that forward-scatters the conduction electrons on their own Fermi surface. We use a combined bosonic and fermionic (Shankar) renormalization group procedure to analyze this effective theory and study the Kondo screening and Fermi surface in the antiferromagnetic phase. The implications for the global magnetic phase diagram, as well as quantum critical points, of heavy fermion metals are discussed.

  17. Understanding the biological responses of nanostructured metals and surfaces

    NASA Astrophysics Data System (ADS)

    Lowe, Terry C.; Reiss, Rebecca A.

    2014-08-01

    Metals produced by Severe Plastic Deformation (SPD) offer distinct advantages for medical applications such as orthopedic devices, in part because of their nanostructured surfaces. We examine the current theoretical foundations and state of knowledge for nanostructured biomaterials surface optimization within the contexts that apply to bulk nanostructured metals, differentiating how their microstructures impact osteogenesis, in particular, for Ultrafine Grained (UFG) titanium. Then we identify key gaps in the research to date, pointing out areas which merit additional focus within the scientific community. For example, we highlight the potential of next-generation DNA sequencing techniques (NGS) to reveal gene and non-coding RNA (ncRNA) expression changes induced by nanostructured metals. While our understanding of bio-nano interactions is in its infancy, nanostructured metals are already being marketed or developed for medical devices such as dental implants, spinal devices, and coronary stents. Our ability to characterize and optimize the biological response of cells to SPD metals will have synergistic effects on advances in materials, biological, and medical science.

  18. Sorption of heavy metals by prepared bacterial cell surfaces

    SciTech Connect

    Churchill, S.A.; Walters, J.V.; Churchill, P.F.

    1995-10-01

    Prepared biomass from two Gram-negative and one Gram-positive bacterial strains was examined for single, binary, and quaternary mixtures of polyvalent metal cation binding to cell surfaces. The biosorption of {sub 24}Cr{sup 3+}, {sub 27}Co{sup 2+}, {sub 28}Ni{sup 2+}, and {sub 29}Cu{sup 2+} for each bacterial cell type was evaluated using a batch equilibrium method. The binding of each metal by all three bacterial cells could be described by the Freundlich sorption model. The isotherm binding constants suggest that E. coli cells are the most efficient at binding copper, chromium, and nickel; and M. luteus adsorbs cobalt most efficiently. The K-values for copper bound to P. aeruginosa and E. coli are > 2-fold and > 8-fold greater, respectively, than previous reported for intact cells. The general metal-affinity series observed was Cr{sup 3+} > Cu{sup 2+} > Ni{sup 2+} > Co{sup 2+}. There was a marked lower affinity of all biosorbents for Co{sup 2+} and Ni{sup 2+}. M. luteus and E. coli had a strong preference for Co{sup 2+} over Ni{sup 2+}. Metal-binding enhancement could be ascribed to increased cell barrier surface porosity to metal-bearing solutions.

  19. Nanotubular surface modification of metallic implants via electrochemical anodization technique

    PubMed Central

    Wang, Lu-Ning; Jin, Ming; Zheng, Yudong; Guan, Yueping; Lu, Xin; Luo, Jing-Li

    2014-01-01

    Due to increased awareness and interest in the biomedical implant field as a result of an aging population, research in the field of implantable devices has grown rapidly in the last few decades. Among the biomedical implants, metallic implant materials have been widely used to replace disordered bony tissues in orthopedic and orthodontic surgeries. The clinical success of implants is closely related to their early osseointegration (ie, the direct structural and functional connection between living bone and the surface of a load-bearing artificial implant), which relies heavily on the surface condition of the implant. Electrochemical techniques for modifying biomedical implants are relatively simple, cost-effective, and appropriate for implants with complex shapes. Recently, metal oxide nanotubular arrays via electrochemical anodization have become an attractive technique to build up on metallic implants to enhance the biocompatibility and bioactivity. This article will thoroughly review the relevance of electrochemical anodization techniques for the modification of metallic implant surfaces in nanoscale, and cover the electrochemical anodization techniques used in the development of the types of nanotubular/nanoporous modification achievable via electrochemical approaches, which hold tremendous potential for bio-implant applications. In vitro and in vivo studies using metallic oxide nanotubes are also presented, revealing the potential of nanotubes in biomedical applications. Finally, an outlook of future growth of research in metallic oxide nanotubular arrays is provided. This article will therefore provide researchers with an in-depth understanding of electrochemical anodization modification and provide guidance regarding the design and tuning of new materials to achieve a desired performance and reliable biocompatibility. PMID:25258532

  20. Nanotubular surface modification of metallic implants via electrochemical anodization technique.

    PubMed

    Wang, Lu-Ning; Jin, Ming; Zheng, Yudong; Guan, Yueping; Lu, Xin; Luo, Jing-Li

    2014-01-01

    Due to increased awareness and interest in the biomedical implant field as a result of an aging population, research in the field of implantable devices has grown rapidly in the last few decades. Among the biomedical implants, metallic implant materials have been widely used to replace disordered bony tissues in orthopedic and orthodontic surgeries. The clinical success of implants is closely related to their early osseointegration (ie, the direct structural and functional connection between living bone and the surface of a load-bearing artificial implant), which relies heavily on the surface condition of the implant. Electrochemical techniques for modifying biomedical implants are relatively simple, cost-effective, and appropriate for implants with complex shapes. Recently, metal oxide nanotubular arrays via electrochemical anodization have become an attractive technique to build up on metallic implants to enhance the biocompatibility and bioactivity. This article will thoroughly review the relevance of electrochemical anodization techniques for the modification of metallic implant surfaces in nanoscale, and cover the electrochemical anodization techniques used in the development of the types of nanotubular/nanoporous modification achievable via electrochemical approaches, which hold tremendous potential for bio-implant applications. In vitro and in vivo studies using metallic oxide nanotubes are also presented, revealing the potential of nanotubes in biomedical applications. Finally, an outlook of future growth of research in metallic oxide nanotubular arrays is provided. This article will therefore provide researchers with an in-depth understanding of electrochemical anodization modification and provide guidance regarding the design and tuning of new materials to achieve a desired performance and reliable biocompatibility.

  1. Fundamental investigations of silane adhesion promoters on metal surfaces

    NASA Astrophysics Data System (ADS)

    Mishra, Sourabh

    1997-08-01

    Silane adhesion promoters are used extensively to enhance bonding of polymers to metals; however, the fundamental bonding mechanisms are not well characterized. In this study, the chemistry of silane bonding to metal surfaces was characterized, and the viability of silanes as adhesion promoters for immobilization of poly(ethylene glycol) on Ti surfaces was determined. The key issues that were addressed are (1) the role of hydroxides in silane bonding on metals, (2) the stability of silanes on metals, (3) the orientation of silanes on Ti, and (4) application of silane as an adhesion promoter between poly(ethylene glycol) (PEG) and Ti. In the first part of the study, bonding of two monofunctional silanes, trimethylmethoxy- and trimethylchloro-silane, was studied on copper surfaces. Polished and silinated surfaces were analyzed using x-ray photoelectron spectroscopy (XPS), glancing angle Fourier transform infrared spectroscopy (FTIR), and atomic force microscopy (AFM). The feasibility of various reactions paths leading to bonding was considered for the two silanes based on the spectroscopic results. Polished Cu surfaces silylated with trimethylmethoxysilane or trimethylchlorosilane were also washed in water to determine the stability of the silane layers. The surfaces were analyzed using XPS. Methoxysilane was found to remain stably bound during washing, whereas chlorosilane was completely washed away. This confirmed that methoxysilanes were probably bound to surface oxides as hydrogen bonded Si-O-R species or metal siloxanes, whereas chlorosilanes could only physisorb because they had removed surface oxides and hydroxyl groups. The silane layers were cured at high temperature in vacuum to promote the formation of metal siloxanes from hydrogen bonded Si-O-R groups. For both silanes, the cured layers were almost completely washed away. The Si-O-R groups in methoxysilane layers were probably converted to less stably bound siloxane dimers during curing. The polished Cu

  2. High surface area graphene-supported metal chalcogenide assembly

    DOEpatents

    Worsley, Marcus A.; Kuntz, Joshua; Orme, Christine A.

    2016-04-19

    A composition comprising at least one graphene-supported assembly, which comprises a three-dimensional network of graphene sheets crosslinked by covalent carbon bonds, and at least one metal chalcogenide compound disposed on said graphene sheets, wherein the chalcogen of said metal chalcogenide compound is selected from S, Se and Te. Also disclosed are methods for making and using the graphene-supported assembly, including graphene-supported MoS.sub.2. Monoliths with high surface area and conductivity can be achieved. Lower operating temperatures in some applications can be achieved. Pore size and volume can be tuned.

  3. STM study of surface structures formed by metal adsorption on semiconductor surfaces

    NASA Astrophysics Data System (ADS)

    Yoon, Myonggeun

    By utilizing a variety of the metal-induced superstructures and growth of metal adsorbates on semiconductor surfaces, we have studied how both the arrangements of atoms in topmost surfaces and the bonding mechanism actually affect both the atomic structures and electronic properties of the surface. This work describes the results of experimental studies of the metal adsorbates on two semiconductor surfaces, Si(111) and Ge(111), using scanning tunneling microscopy (STM), large modulation-amplitude local-barrier-height (LM-LBH) imaging as primary tools for structural analysis, and scanning tunneling spectroscopy (STS) as a tool for electronic analysis. Firstly, we have obtained new real-space images of the filled dangling-bond states of the alkali-metal induced 3x1 reconstruction of the Si(111) surface associated with a recently proposed Si=Si double-bond stabilized surface structure. Our new experimental evidence reveals significant subtle differences between this local bonding on Na/Si(111)-(3x1) and Na/Ge(111)-(3x1) which argues a strong case for a previously proposed "Honeycomb-chain-channel model" but with a relaxation of a strict double-bond requirement, particularly on the Ge surface. Secondly, the adsorption mechanism and the origin of the In, Al & Sn-induced surface electronic states on the Si(111)-(7x7) surface have been studied using bias-dependent scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS). Our experimental evidence suggests that all these metal atoms are covalently bonding with Si topmost atoms on Si(111)-(7x7) surface while In and Al atoms possibly substitute for Si adatoms in the 7x7 unit cell during room temperature adsorption. Both mechanisms remove intrinsic metallic surface states caused by partially occupied Si adatom dangling bonds, opening a bandgap at the surface and producing a metal-insulator transition. Finally, we report on the self-assembly of a superlattice of nanodots of different elements (Sn, In) on a

  4. Surface modes at metallic an photonic crystal interfaces

    SciTech Connect

    Dai, Weitao

    2009-01-01

    A surface mode is an electromagnetic field distribution bounded at a surface. It decays exponentially with the distance from the surface on both sides of the surface and propagates at the surface. The surface mode exists at a metal-dielectric interface as surface plasmon (1) or at a photonic crystal surface terminated properly (34; 35; 36). Besides its prominent near-filed properties, it can connect structures at its propagation surface and results in far-field effects. Extraordinary transmission (EOT) and beaming are two examples and they are the subjects I am studying in this thesis. EOT means the transmission through holes in an opaque screen can be much larger than the geometrical optics limitation. Based on our everyday experience about shadows, the transmission equals the filling ratio of the holes in geometrical optics. The conventional diffraction theory also proved that the transmission through a subwavelength circular hole in an infinitely thin perfect electric conductor (PEC) film converges to zero when the hole's dimension is much smaller than the wavelength (40). Recently it is discovered that the transmission can be much larger than the the filling ratio of the holes at some special wavelengths (41). This cannot be explained by conventional theories, so it is called extraordinary transmission. It is generally believed that surface plasmons play an important role (43; 44) in the EOT through a periodic subwavelength hole array in a metallic film. The common theories in literatures are based on these arguments. The surface plasmons cannot be excited by incident plane waves directly because of momentum mismatch. The periodicity of the hole arrays will provide addition momentum. When the momentum-matching condition of surface plasmons is satisfied, the surface plasmons will be excited. Then these surface plasmons will collect the energy along the input surface and carry them to the holes. So the transmission can be bigger than the filling ratio. Based on

  5. Radiation Induced Surface Activity Phenomenon: 1. Report - Surface Wettability on Metal Oxides

    SciTech Connect

    Yasuyuki Imai; Tatsuya Koga; Tomoji Takamasa; Koji Okamoto; Susumu Uematsu

    2002-07-01

    Improving the limit of boiling heat transfer or critical heat flux requires that the cooling liquid can contact the heating surface, or a high-wettability, highly hydrophilic heating surface, even if a vapor bubble layer is generated on the surface. We investigated surface wettability using metal oxides irradiated by gamma rays in room condition. Contact angle, an indicator of macroscopic wettability, was measured by image processing of the images obtained by a CCD video camera. The results showed that the surface wettability on oxide metal pieces of titanium, zircaloy No. 4, SUS-304 and copper improved significantly by Radiation Induced Surface Activity (RISA) phenomenon. Highly hydrophilic conditions on the test pieces were achieved after 500 kGy irradiation of {sup 60}Co gamma ray. (authors)

  6. Surface imaging of metallic material fractures using optical coherence tomography.

    PubMed

    Hutiu, Gheorghe; Duma, Virgil-Florin; Demian, Dorin; Bradu, Adrian; Podoleanu, Adrian Gh

    2014-09-10

    We demonstrate the capability of optical coherence tomography (OCT) to perform topography of metallic surfaces after being subjected to ductile or brittle fracturing. Two steel samples, OL 37 and OL 52, and an antifriction Sn-Sb-Cu alloy were analyzed. Using an in-house-built swept source OCT system, height profiles were generated for the surfaces of the two samples. Based on such profiles, it can be concluded that the first two samples were subjected to ductile fracture, while the third one was subjected to brittle fracture. The OCT potential for assessing the surface state of materials after fracture was evaluated by comparing OCT images with images generated using an established method for such investigations, scanning electron microscopy (SEM). Analysis of cause of fracture is essential in response to damage of machinery parts during various accidents. Currently the analysis is performed using SEM, on samples removed from the metallic parts, while OCT would allow in situ imaging using mobile units. To the best of our knowledge, this is the first time that the OCT capability to replace SEM has been demonstrated. SEM is a more costly and time-consuming method to use in the investigation of surfaces of microstructures of metallic materials.

  7. Wireless Metal Detection and Surface Coverage Sensing for All-Surface Induction Heating

    PubMed Central

    Kilic, Veli Tayfun; Unal, Emre; Demir, Hilmi Volkan

    2016-01-01

    All-surface induction heating systems, typically comprising small-area coils, face a major challenge in detecting the presence of a metallic vessel and identifying its partial surface coverage over the coils to determine which of the coils to power up. The difficulty arises due to the fact that the user can heat vessels made of a wide variety of metals (and their alloys). To address this problem, we propose and demonstrate a new wireless detection methodology that allows for detecting the presence of metallic vessels together with uniquely sensing their surface coverages while also identifying their effective material type in all-surface induction heating systems. The proposed method is based on telemetrically measuring simultaneously inductance and resistance of the induction coil coupled with the vessel in the heating system. Here, variations in the inductance and resistance values for an all-surface heating coil loaded by vessels (made of stainless steel and aluminum) at different positions were systematically investigated at different frequencies. Results show that, independent of the metal material type, unique identification of the surface coverage is possible at all freqeuncies. Additionally, using the magnitude and phase information extracted from the coupled coil impedance, unique identification of the vessel effective material is also achievable, this time independent of its surface coverage. PMID:26978367

  8. Wireless Metal Detection and Surface Coverage Sensing for All-Surface Induction Heating.

    PubMed

    Kilic, Veli Tayfun; Unal, Emre; Demir, Hilmi Volkan

    2016-03-11

    All-surface induction heating systems, typically comprising small-area coils, face a major challenge in detecting the presence of a metallic vessel and identifying its partial surface coverage over the coils to determine which of the coils to power up. The difficulty arises due to the fact that the user can heat vessels made of a wide variety of metals (and their alloys). To address this problem, we propose and demonstrate a new wireless detection methodology that allows for detecting the presence of metallic vessels together with uniquely sensing their surface coverages while also identifying their effective material type in all-surface induction heating systems. The proposed method is based on telemetrically measuring simultaneously inductance and resistance of the induction coil coupled with the vessel in the heating system. Here, variations in the inductance and resistance values for an all-surface heating coil loaded by vessels (made of stainless steel and aluminum) at different positions were systematically investigated at different frequencies. Results show that, independent of the metal material type, unique identification of the surface coverage is possible at all freqeuncies. Additionally, using the magnitude and phase information extracted from the coupled coil impedance, unique identification of the vessel effective material is also achievable, this time independent of its surface coverage.

  9. Helium atmospheric pressure plasma jets touching dielectric and metal surfaces

    SciTech Connect

    Norberg, Seth A. Johnsen, Eric; Kushner, Mark J.

    2015-07-07

    Atmospheric pressure plasma jets (APPJs) are being investigated in the context plasma medicine and biotechnology applications, and surface functionalization. The composition of the surface being treated ranges from plastics, liquids, and biological tissue, to metals. The dielectric constant of these materials ranges from as low as 1.5 for plastics to near 80 for liquids, and essentially infinite for metals. The electrical properties of the surface are not independent variables as the permittivity of the material being treated has an effect on the dynamics of the incident APPJ. In this paper, results are discussed from a computational investigation of the interaction of an APPJ incident onto materials of varying permittivity, and their impact on the discharge dynamics of the plasma jet. The computer model used in this investigation solves Poisson's equation, transport equations for charged and neutral species, the electron energy equation, and the Navier-Stokes equations for the neutral gas flow. The APPJ is sustained in He/O{sub 2} = 99.8/0.2 flowing into humid air, and is directed onto dielectric surfaces in contact with ground with dielectric constants ranging from 2 to 80, and a grounded metal surface. Low values of relative permittivity encourage propagation of the electric field into the treated material and formation and propagation of a surface ionization wave. High values of relative permittivity promote the restrike of the ionization wave and the formation of a conduction channel between the plasma discharge and the treated surface. The distribution of space charge surrounding the APPJ is discussed.

  10. Interaction of fast charges with a rough metal surface

    NASA Astrophysics Data System (ADS)

    Lyon, Keenan; Zhang, Ying-Ying; Mišković, Z. L.; Song, Yuan-Hong; Wang, You-Nian

    2015-09-01

    We use the Green function formulation of a dielectric response formalism to study the dynamic polarization of a rough metal surface by a single charged particle and by a pair of charged particles that move parallel to the surface. While the surface roughness is treated nonperturbatively, the plasmon excitation of the metal electron gas is described locally. We find that the magnitudes of both the image potential and the stopping power of a single particle are increased by the increasing roughness and decreasing correlation length of the surface. On the other hand, both the long-range wake potential of a single charged particle and the interaction potential between two particles are weakly affected by the surface roughness. However, the strongest effects of the surface roughness are seen in the correlated stopping power of two charged particles, giving rise to oscillations in the dependence of the stopping ratio on their distance, both when the interparticle axis is perpendicular to their direction of motion and when the wake-related oscillations are damped by adiabatic suppression of plasmon excitations at low particle speeds.

  11. Multifunctional methacrylate-based coatings for glass and metal surfaces

    NASA Astrophysics Data System (ADS)

    Pospiech, Doris; Jehnichen, Dieter; Starke, Sandra; Müller, Felix; Bünker, Tobias; Wollenberg, Anne; Häußler, Liane; Simon, Frank; Grundke, Karina; Oertel, Ulrich; Opitz, Michael; Kruspe, Rainer

    2017-03-01

    In order to prevent freshwater biofouling glass and metal surfaces were coated with novel transparent methacrylate-based copolymers. The multifunctionality of the copolymers, such as adhesion to the substrate, surface polarity, mechanical long-term stability in water, and ability to form metal complexes was inserted by the choice of suitable comonomers. The monomer 2-acetoacetoxy ethyl methacrylate (AAMA) was used as complexing unit to produce copper(II) complexes in the coating's upper surface layer. The semifluorinated monomer 1H,1H,2H,2H-perfluorodecyl methacrylate was employed to adjust the surface polarity and wettability. Comprehensive surface characterization techniques, such as X-ray photoelectron spectroscopy (XPS) and contact angle measurements showed that surface compositions and properties can be easily adjusted by varying the concentrations of the comonomers. The formation of copper(II) complexes along the copolymer chains and their stability against washing out with plenty of water was proven by XPS. Copolymers containing semifluorinated comonomers significantly inhibited the growth of Achnanthidium species. Copolymers with copper-loaded AAMA-sequences were able to reduce both the growth of Achnanthidium spec. and Staphylococcus aureus.

  12. Origins of Folding Instabilities on Polycrystalline Metal Surfaces

    NASA Astrophysics Data System (ADS)

    Beckmann, N.; Romero, P. A.; Linsler, D.; Dienwiebel, M.; Stolz, U.; Moseler, M.; Gumbsch, P.

    2014-12-01

    Wear and removal of material from polycrystalline metal surfaces is inherently connected to plastic flow. Here, plowing-induced unconstrained surface plastic flow on a nanocrystalline copper surface has been studied by massive molecular dynamics simulations and atomic force microscopy scratch experiments. In agreement with experimental findings, bulges in front of a model asperity develop into vortexlike fold patterns that mark the disruption of laminar flow. We identify dislocation-mediated plastic flow in grains with suitably oriented slip systems as the basic mechanism of bulging and fold formation. The observed folding can be fundamentally explained by the inhomogeneity of plasticity on polycrystalline surfaces which favors bulge formation on grains with suitably oriented slip system. This process is clearly distinct from Kelvin-Helmholtz instabilities in fluids, which have been previously suggested to resemble the formed surface fold patterns. The generated prow grows into a rough chip with stratified lamellae that are identified as the precursors of wear debris. Our findings demonstrate the importance of surface texture and grain structure engineering to achieve ultralow wear in metals.

  13. Free surface stability of liquid metal plasma facing components

    NASA Astrophysics Data System (ADS)

    Fiflis, P.; Christenson, M.; Szott, M.; Kalathiparambil, K.; Ruzic, D. N.

    2016-10-01

    An outstanding concern raised over the implementation of liquid metal plasma facing components in fusion reactors is the potential for ejection of liquid metal into the fusion plasma. The influences of Rayleigh-Taylor-like and Kelvin-Helmholtz-like instabilities were experimentally observed and quantified on the thermoelectric-driven liquid-metal plasma-facing structures (TELS) chamber at the University of Illinois at Urbana-Champaign. To probe the stability boundary, plasma currents and velocities were first characterized with a flush probe array. Subsequent observations of lithium ejection under exposure in the TELS chamber exhibited a departure from previous theory based on linear perturbation analysis. The stability boundary is mapped experimentally over the range of plasma impulses of which TELS is capable to deliver, and a new theory based on a modified set of the shallow water equations is presented which accurately predicts the stability of the lithium surface under plasma exposure.

  14. Surface plasmon mode analysis of nanoscale metallic rectangular waveguide.

    PubMed

    Kong, Fanmin; Wu, Bae-Ian; Chen, Hongsheng; Kong, Jin Au

    2007-09-17

    A detailed study of guided modes in a nanoscale metallic rectangular waveguide is presented by using the effective dielectric constant approach. The guided modes, including both traditional waveguide mode and surface plasmon mode, are investigated for the silver rectangular waveguide. The mode evolution in narrow waveguide is also discussed with the emphasis on the dependence of mode dispersion with waveguide height. Finally, the red-shift of the cutoff wavelength of the fundamental mode is observed when the waveguide height decreases, contrary to the behavior of regular metallic waveguide with PEC boundary. The comprehensive analysis can provide some guideline in the design of subwavelength optical devices based on the dispersion characteristics of metallic rectangular bore.

  15. Electronic friction near metal surfaces: A case where molecule-metal couplings depend on nuclear coordinates

    NASA Astrophysics Data System (ADS)

    Dou, Wenjie; Subotnik, Joseph E.

    2017-03-01

    We derive an explicit form for the electronic friction as felt by a molecule near a metal surface for the general case that molecule-metal couplings depend on nuclear coordinates. Our work generalizes a previous study by von Oppen et al. [Beilstein J. Nanotechnol. 3, 144 (2012)], where we now go beyond the Condon approximation (i.e., molecule-metal couplings are not held constant). Using a non-equilibrium Green's function formalism in the adiabatic limit, we show that fluctuating metal-molecule couplings lead to new frictional damping terms and random forces, plus a correction to the potential of mean force. Numerical tests are performed and compared with a modified classical master equation; our results indicate that violating the Condon approximation can have a large effect on dynamics.

  16. [Metal on metal bearing surfaces in total hip arthroplasty: a survey of material incidents].

    PubMed

    Passuti, N; Terver, S

    2007-05-01

    This study is dedicated to the problems met with metal-metal bearing prostheses. We have analysed the results of the reports sent to the AFSSAPS relating incidents described with this interface. Only 11 incidents were reported during the last 4 years by surgeons from different centers in France. At a mean follow-up of 7 years, we collected 2614 total hip arthroplasties with metal-metal bearings and among them only 5 cases of unusual osteolysis and 10 cases of impingement. The bibliographic analysis did not show any severe specific complication due to the release of Cobalt or Chromium ions. The increased levels of Co an Cr in the patients' blood is now a well established notion (with more than 10 years follow up) and no special carcinogenetic effect has been correlated with the metal-metal bearings. Small diameter cemented cups can provide complications with high rates of acetabular loosening and metallosis; the same is true for some cementless cups also with loosening and a high revision rate. Among 143 hip prosthesis with a cemented polyethylene cup, at a mean follow-up of 42 months there were 22% of evolutive radiolucencies around the cups concerning all three De Lee and Charnley zones. Furthermore there was a statistically significant difference between small and large diameter cups (loosening of cups less than 46 mm in diameter). The same problem has been described for some cementless cups with loosening at the metal-bone interface due to a failure of osteointegration at the implant surface. However no failures were observed with an hydroxyapatite coating on the same cup. An other matter of concern is the skirted metal head: this design is responsible for a high rate of impingement and of prosthetic revision (2.3% among 642 THA). In these cases the increase of Cobalt serum levels was well correlated with the failure of the metal-metal interface. Large diameter heads decrease significantly the risks of dislocation. This is correlated with the increase in size

  17. The Interaction of Hydrogen with Simple and Noble Metals Surfaces

    NASA Astrophysics Data System (ADS)

    Sprunger, Phillip T.

    The basic concepts of adsorption are illustrated by the investigation of a simple adsorbate (hydrogen) with the "simplest" metals (simple and noble metals). Theoretically tractable, these systems serve as an excellent test of our basic understanding of chemisorption. The interaction of atomic and molecular hydrogen with the surfaces of Mg(0001), Mg(1120), Li(110), K(110), Ag(110), and Ag(111) have been studied with a variety of experimental probes. In all cases, no evidence for H_2 associative or dissociative adsorption is observed at the substrate temperature investigated (>=q90 K). In the case of the simple metals below 150 K, atomic hydrogen is bound to the surfaces in a strongly chemisorbed state (hydride). For Mg and Li, the hydride is localized to the surface wherein the substrate electron density is lower than the bulk. Because of the low electron density, hydrogen is absorbed into the bulk of K at low temperatures and forms a bulk-hydride phase. However, these low-temperature phases are metastable. In the case of Mg, hydrogen moves into lower energy configuration bonding sites which are closer to or below the surface plane. However, the hydride characteristics are absent; the H atom is effectively screened because of the higher jellium density. In contrast, upon annealing, hydrogen is absorbed into the bulk of Li and K and phase separation occurs forming regions of clean metal and bulk hydride areas. The results are compared to theoretical studies; the propensity for absorption over adsorption is understood in terms of jellium-based models. In the case of silver, at 100 K, atomic hydrogen bonds in trigonal sites on both the (110) and (111) surfaces. As a function of H concentration, a sequence of lattice gas superstructures is observed; these phases are accompanied by small H-induced displacements of the substrate surface atoms. In the case of Ag(110), the low-temperature phase is metastable; upon annealing, hydrogen desorption from low energy states is

  18. Method for Reduction of Silver Biocide Plating on Metal Surfaces

    NASA Technical Reports Server (NTRS)

    Steele, John; Nalette, Timothy; Beringer, Durwood

    2013-01-01

    Silver ions in aqueous solutions (0.05 to 1 ppm) are used for microbial control in water systems. The silver ions remain in solution when stored in plastic containers, but the concentration rapidly decreases to non-biocidal levels when stored in metal containers. The silver deposits onto the surface and is reduced to non-biocidal silver metal when it contacts less noble metal surfaces, including stainless steel, titanium, and nickel-based alloys. Five methods of treatment of contact metal surfaces to deter silver deposition and reduction are proposed: (1) High-temperature oxidation of the metal surface; (2) High-concentration silver solution pre-treatment; (3) Silver plating; (4) Teflon coat by vapor deposition (titanium only); and (5) A combination of methods (1) and (2), which proved to be the best method for the nickel-based alloy application. The mechanism associated with surface treatments (1), (2), and (5) is thought to be the development of a less active oxide layer that deters ionic silver deposition. Mechanism (3) is an attempt to develop an equilibrium ionic silver concentration via dissolution of metallic silver. Mechanism (4) provides a non-reactive barrier to deter ionic silver plating. Development testing has shown that ionic silver in aqueous solution was maintained at essentially the same level of addition (0.4 ppm) for up to 15 months with method (5) (a combination of methods (1) and (2)), before the test was discontinued for nickel-based alloys. Method (1) resulted in the maintenance of a biocidal level (approximately 0.05 ppm) for up to 10 months before that test was discontinued for nickel-based alloys. Methods (1) and (2) used separately were able to maintain ionic silver in aqueous solution at essentially the same level of addition (0.4 ppm) for up to 10 months before the test was discontinued for stainless steel alloys. Method (3) was only utilized for titanium alloys, and was successful at maintaining ionic silver in aqueous solution at

  19. Ultrasonic characterization of shot-peened metal surfaces

    NASA Astrophysics Data System (ADS)

    Lavrentyev, Anton I.; Veronesi, William A.

    2001-08-01

    Shot peening is a well-known method for extending the fatigue life of metal components by introducing near-surface compressive residual stresses. The capability to nondestructively evaluate near-surface residual stress would greatly aid the assurance of proper fatigue life in shot-peened components. This paper describes our work on near-surface residual stress measurement by an ultrasonic surface wave method. In this method, a variation of ultrasonic surface wave speed with shot peening intensity is measured. Since the effective wave penetration depth is inversely related to the excitation frequency, the method has the potential to provide the stress-depth profile. The paper presents results from an ultrasonic characterization study of shot peened Al-7075 and Waspaloy surfaces. Rayleigh wave velocity measurements by a V(z)-curve method were made on smooth and shot peened samples using line-focus ultrasonic transducers. Several factors were found to contribute to the surface wave velocity measurements: surface roughness, near-surface grain reorientation (texture), dislocation density increase, and residual stress. In this paper we estimate quantitatively the effects of each factor and discuss how these effects can be separated and accounted for during residual stress measurement.

  20. A Liquid Metal Flume for Free Surface Magnetohydrodynamic Experiments

    SciTech Connect

    Nornberg, M.D.; Ji, H.; Peterson, J.L.; Rhoads, J.R.

    2008-08-27

    We present an experiment designed to study magnetohydrodynamic effects in free-surface channel flow. The wide aspect ratio channel (the width to height ratio is about 15) is completely enclosed in an inert atmosphere to prevent oxidization of the liquid metal. A custom-designed pump reduces entrainment of oxygen, which was found to be a problem with standard centrifugal and gear pumps. Laser Doppler Velocimetry experiments characterize velocity profiles of the flow. Various flow constraints mitigate secondary circulation and end effects on the flow. Measurements of the wave propagation characteristics in the liquid metal demonstrate the surfactant effect of surface oxides and the damping of fluctuations by a cross-channel magnetic field.

  1. Inelastic low energy electron diffraction at metal surfaces

    NASA Astrophysics Data System (ADS)

    Nazarov, V. U.; Nishigaki, S.

    2001-06-01

    The role of incident electrons penetration under a metal surface in electron energy loss spectroscopy is considered within the fully quantum-mechanical approach. The stabilized jellium model of the surface in the semi-infinite geometry and the time-dependent local density approximation for the dynamical response are used. The travel of the projectile electron inside the target metal is treated within the kinematic low energy electron diffraction theory. Confirming our simplified hard-wall reflection model results [Phys. Rev. B 59 (1999) 9866], the dramatic enhancement of the multipole plasmon peak as compared with the dipole-mode calculations is obtained for Na and Cs, which is in a qualitative agreement with the experiment. However, for K the calculation fails to explain the experiment, which discrepancy is discussed and the future improvements of the method are outlined.

  2. Adventitious Carbon on Primary Sample Containment Metal Surfaces

    NASA Technical Reports Server (NTRS)

    Calaway, M. J.; Fries, M. D.

    2015-01-01

    Future missions that return astromaterials with trace carbonaceous signatures will require strict protocols for reducing and controlling terrestrial carbon contamination. Adventitious carbon (AC) on primary sample containers and related hardware is an important source of that contamination. AC is a thin film layer or heterogeneously dispersed carbonaceous material that naturally accrues from the environment on the surface of atmospheric exposed metal parts. To test basic cleaning techniques for AC control, metal surfaces commonly used for flight hardware and curating astromaterials at JSC were cleaned using a basic cleaning protocol and characterized for AC residue. Two electropolished stainless steel 316L (SS- 316L) and two Al 6061 (Al-6061) test coupons (2.5 cm diameter by 0.3 cm thick) were subjected to precision cleaning in the JSC Genesis ISO class 4 cleanroom Precision Cleaning Laboratory. Afterwards, the samples were analyzed by X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy.

  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. Improved Method Being Developed for Surface Enhancement of Metallic Materials

    NASA Technical Reports Server (NTRS)

    Gabb, Timothy P.; Telesman, Jack; Kantzos, Peter T.

    2001-01-01

    Surface enhancement methods induce a layer of beneficial residual compressive stress to improve the impact (FOD) resistance and fatigue life of metallic materials. A traditional method of surface enhancement often used is shot peening, in which small steel spheres are repeatedly impinged on metallic surfaces. Shot peening is inexpensive and widely used, but the plastic deformation of 20 to 40 percent imparted by the impacts can be harmful. This plastic deformation can damage the microstructure, severely limiting the ductility and durability of the material near the surface. It has also been shown to promote accelerated relaxation of the beneficial compressive residual stresses at elevated temperatures. Low-plasticity burnishing (LPB) is being developed as an improved method for the surface enhancement of metallic materials. LPB is being investigated as a rapid, inexpensive surface enhancement method under NASA Small Business Innovation Research contracts NAS3-98034 and NAS3-99116, with supporting characterization work at NASA. Previously, roller burnishing had been employed to refine surface finish. This concept was adopted and then optimized as a means of producing a layer of compressive stress of high magnitude and depth, with minimal plastic deformation (ref. 1). A simplified diagram of the developed process is given in the following figure. A single pass of a smooth, free-rolling spherical ball under a normal force deforms the surface of the material in tension, creating a compressive layer of residual stress. The ball is supported in a fluid with sufficient pressure to lift the ball off the surface of the retaining spherical socket. The ball is only in mechanical contact with the surface of the material being burnished and is free to roll on the surface. This apparatus is designed to be mounted in the conventional lathes and vertical mills currently used to machine parts. The process has been successfully applied to nickel-base superalloys by a team from the

  5. Intermediate Compounds Formed on Metal Surfaces during Catalysis

    NASA Astrophysics Data System (ADS)

    Tanaka, K.

    An idea of the formation of specific compounds over the metal surfaces has been applied to the metal surfaces during catalysis. One is the formation of c(2 × 2)-N overlayer on Pd(100). Rh(100) and Pt-Rh(100) surfaces during the reaction of NO with H_2, that is, these metals make no bulk nitrides and are inactive for the adsorption of N_2. These c(2 × 2)-N overlayers undergo the hydrogenation in the presence of H_2, and the high resolution electron energy loss spectrum (HREELS) shows the formation of NH_x species. Intensity of the energy loss peak for the N-H vibration depends on a half order in hydrogen pressure which indicates the establishment of an equilibration of N + 1/2H_{2} {rightleftarrows} NH during the hydrogenation reaction. Another example is the formation of carbide overlayer on Ni(100) and Ni(111) surfaces. It was shown that the carbide overlayer on Ni(111) surface takes same structure as that of the p4g carbide overlayer on Ni(100) surface, which may give a persuasive explanation to the structure insensitive methanation reaction on Ni(100) and Ni(111) surfaces. Finally, more direct evidence for the formation of surface compounds is given by the scanning tunneling microscopy (STM) works on Ag(110) surface. When Ag(110) surface is exposed to O_2 at room temperature, rapid growth of AgO chain in parallel to the <001> direction was observed by STM, and the AgO chains are arranged by making p(n × 1) ordered structures over the Ag(110) surface. The ordered phases of AgO chains make one-dimensional phase boundaries, and it was found that the boundary of the two phases necessarily makes a fluctuated structure. The atom model for the two-dimensional arrangement of the AgO chains proves the formation of energetically degenerated sites at the boundary, which is responsible to the fluctuated boundary structures.

  6. Molecular metal catalysts on supports: organometallic chemistry meets surface science.

    PubMed

    Serna, Pedro; Gates, Bruce C

    2014-08-19

    Recent advances in the synthesis and characterization of small, essentially molecular metal complexes and metal clusters on support surfaces have brought new insights to catalysis and point the way to systematic catalyst design. We summarize recent work unraveling effects of key design variables of site-isolated catalysts: the metal, metal nuclearity, support, and other ligands on the metals, also considering catalysts with separate, complementary functions on supports. The catalysts were synthesized with the goal of structural simplicity and uniformity to facilitate incisive characterization. Thus, they are essentially molecular species bonded to porous supports chosen for their high degree of uniformity; the supports are crystalline aluminosilicates (zeolites) and MgO. The catalytic species are synthesized in reactions of organometallic precursors with the support surfaces; the precursors include M(L)2(acetylacetonate)1-2, with M = Ru, Rh, Ir, or Au and the ligands L = C2H4, CO, or CH3. Os3(CO)12 and Ir4(CO)12 are used as precursors of supported metal clusters, and some such catalysts are made by ship-in-a-bottle syntheses to trap the clusters in zeolite cages. The simplicity and uniformity of the supported catalysts facilitate precise structure determinations, even in reactive atmospheres and during catalysis. The methods of characterizing catalysts in reactive atmospheres include infrared (IR), extended X-ray absorption fine structure (EXAFS), X-ray absorption near edge structure (XANES), and nuclear magnetic resonance (NMR) spectroscopies, and complementary methods include density functional theory and atomic-resolution aberration-corrected scanning transmission electron microscopy for imaging of individual metal atoms. IR, NMR, XANES, and microscopy data demonstrate the high degrees of uniformity of well-prepared supported species. The characterizations determine the compositions of surface metal complexes and clusters, including the ligands and the metal

  7. Formation of Organometallic Intermediate States in On-Surface Ullmann Couplings.

    PubMed

    Barton, Dennis; Gao, Hong-Ying; Held, Philipp Alexander; Studer, Armido; Fuchs, Harald; Doltsinis, Nikos L; Neugebauer, Johannes

    2017-02-17

    Possible origins of the formation of organometallic intermediates in on-surface Ullmann couplings have been investigated by surface tunneling microscopy (STM) and density functional theory (DFT) calculations. We consider the case of iodobenzenes on the coinage metals Au, Ag and Cu. We found experimental evidence for the formation of surface vacancies and the presence of metal adatoms in these coupling reactions, which are taken as a hint for the reactive extraction of surface atoms by adsorbates. In a second step, we demonstrate by ab initio molecular dynamics calculations for aryl-iodides on copper that metal atoms can be pulled out of the surface to form metalorganic species. By contrast, a thermally activated provision of a metal atom from the surface to form an adatom is energetically unfavourable. Finally, we investigate the mechanism and energetics of the reactive extraction of surface metal atoms by means of (climbing-image) nudged-elastic-band density-functional theory calculations for iodobenzene on copper, silver and gold, and analyze our results in the light of the experimental findings.

  8. Single-molecule chemistry of metal phthalocyanine on noble metal surfaces.

    PubMed

    Li, Zhenyu; Li, Bin; Yang, Jinlong; Hou, Jian Guo

    2010-07-20

    To develop new functional materials and nanoscale electronics, researchers would like to accurately describe and precisely control the quantum state of a single molecule on a surface. Scanning tunneling microscopy (STM), combined with first-principles simulations, provides a powerful technique for acquiring this level of understanding. Traditionally, metal phthalocyanine (MPc) molecules, composed of a metal atom surrounded by a ligand ring, have been used as dyes and pigments. Recently, MPc molecules have shown great promise as components of light-emitting diodes, field-effect transistors, photovoltaic cells, and single-molecule devices. In this Account, we describe recent research on the characterization and control of adsorption and electronic states of a single MPc molecule on noble metal surfaces. In general, the electronic and magnetic properties of a MPc molecule largely depend on the type of metal ion within the phthalocyanine ligand and the type of surface on which the molecule is adsorbed. However, with the STM technique, we can use on-site molecular "surgery" to manipulate the structure and the properties of the molecule. For example, STM can induce a dehydrogenation reaction of the MPc, which allows us to control the Kondo effect, which describes the spin polarization of the molecule and its interaction with the complex environment. A specially designed STM tip can allow researchers to detect certain molecule-surface hybrid states that are not accessible by other techniques. By matching the local orbital symmetry of the STM tip and the molecule, we can generate the negative differential resistance effect in the formed molecular junction. This orbital symmetry based mechanism is extremely robust and does not critically depend on the geometry of the STM tip. In summary, this simple model system, a MPc molecule absorbed on a noble metal surface, demonstrates the power of STM for quantum characterization and manipulation of single molecules, highlighting the

  9. In situ surface-enhanced Raman spectroscopy of monodisperse silver nanowire arrays

    NASA Astrophysics Data System (ADS)

    Sauer, G.; Brehm, G.; Schneider, S.; Graener, H.; Seifert, G.; Nielsch, K.; Choi, J.; Göring, P.; Gösele, U.; Miclea, P.; Wehrspohn, R. B.

    2005-01-01

    Highly ordered two-dimensional arrays of monodisperse coinage metal nanowires embedded in an alumina matrix have been prepared. When light is propagating in the direction of the long axis of the nanowire, plasmon-enhanced absorption and light guidance of the nanowire were observed by optical microspectroscopy and scanning near-field optical spectroscopy and compared to Mie scattering theory. By selectively dissolving the matrix at a constant etching rate, we detected in situ and ex situ the surface-enhanced Raman scattering (SERS) of organic dyes. In contrast to earlier publications, we find that the SERS signal is linearly proportional to the free-surface area of the nanowires that are in contact with the dye. We cannot detect any change in the enhancement factor due to the releasing of the nanowires from the host structure.

  10. Method of inducing surface ensembles on a metal catalyst

    DOEpatents

    Miller, S.S.

    1987-10-02

    A method of inducing surface ensembles on a transition metal catalyst used in the conversion of a reactant gas or gas mixture, such as carbon monoxide and hydrogen into hydrocarbons (the Fischer-Tropsch reaction) is disclosed which comprises adding a Lewis base to the syngas (CO + H/sub 2/) mixture before reaction takes place. The formation of surface ensembles in this manner restricts the number and types of reaction pathways which will be utilized, thus greatly narrowing the product distribution and maximizing the efficiency of the Fischer-Tropsch reaction. Similarly, amines may also be produced by the conversion of reactant gas or gases, such as nitrogen, hydrogen, or hydrocarbon constituents.

  11. Protective coatings of metal surfaces by cold plasma treatment

    NASA Technical Reports Server (NTRS)

    Manory, R.; Grill, A.

    1985-01-01

    The cold plasma techniques for deposition of various types of protective coatings are reviewed. The main advantage of these techniques for deposition of ceramic films is the lower process temperature, which enables heat treating of the metal prior to deposition. In the field of surface hardening of steel, significant reduction of treatment time and energy consumption were obtained. A simple model for the plasma - surface reactions in a cold plasma system is presented, and the plasma deposition techniques are discussed in view of this model.

  12. Activated Metal Oxide Surfaces as Highly Reactive Environments

    DTIC Science & Technology

    1990-08-03

    underway. " Synthesis of Ultra-High Surface Area Fe203 by Precipitation Methods Yong-Xi Li A series of precipitations of Fe(OH) 3 (from FeCl 3) at...Progress was also made on developing new aerogel procedures for synthesis of ultra-high surface area magnesium oxide. Finally,’ome metal oxide molecules...were studied in chemical reactions and by theoretical methods .-) Three students earned Ph.D. degrees and one an M.S. degree. A visiting professor and

  13. Molecular switches from benzene derivatives adsorbed on metal surfaces

    PubMed Central

    Liu, Wei; Filimonov, Sergey N.; Carrasco, Javier; Tkatchenko, Alexandre

    2013-01-01

    Transient precursor states are often experimentally observed for molecules adsorbing on surfaces. However, such precursor states are typically rather short-lived, quickly yielding to more stable adsorption configurations. Here we employ first-principles calculations to systematically explore the interaction mechanism for benzene derivatives on metal surfaces, enabling us to selectively tune the stability and the barrier between two metastable adsorption states. In particular, in the case of the tetrachloropyrazine molecule, two equally stable adsorption states are identified with a moderate and conceivably reversible barrier between them. We address the feasibility of experimentally detecting the predicted bistable behaviour and discuss its potential usefulness in a molecular switch. PMID:24157660

  14. Laser-Driven Corrugation Instability of Liquid Metal Surfaces

    NASA Astrophysics Data System (ADS)

    Keilmann, Fritz

    1983-12-01

    During intense CO2-laser irradiation deep corrugations build up on liquid metals such as Hg, In, Sn, Al, and Pb. Spacing, orientation, growth, and decay of the corrugations are studied, by visible light diffraction; support is found for a model of stimulated scattering where the incident light parametrically decays into both the surface corrugation and a surface plasmon. Thermal evaporation supplies the nonlinearity. The instability provides polarization-dependent absorption and can be expected in laser-metalworking and laser-plasma situations.

  15. Method for removal of furfural coke from metal surfaces

    SciTech Connect

    Turner, J.D.

    1990-02-27

    This patent describes a process for preparing furfural coke for removal from metallic surfaces. It comprises: heating ship furfural coke without causing an evolution of heat capable of undesirably altering metallurgical properties of the surfaces in the presence of a gas with a total pressure of less than 100 psig containing molecular oxygen. The gas being at a sufficient temperature below 800{degrees}F. (427{degrees}C.) for a sufficient time to change the crush strength of the coke so as to permit removal with a water jet at a pressure of about 5000 psi.

  16. Method of inducing surface ensembles on a metal catalyst

    DOEpatents

    Miller, Steven S.

    1989-01-01

    A method of inducing surface ensembles on a transition metal catalyst used in the conversion of a reactant gas or gas mixture, such as carbon monoxide and hydrogen into hydrocarbons (the Fischer-Tropsch reaction) is disclosed which comprises adding a Lewis base to the syngas (CO+H.sub.2) mixture before reaction takes place. The formation of surface ensembles in this manner restricts the number and types of reaction pathways which will be utilized, thus greatly narrowing the product distribution and maximizing the efficiency of the Fischer-Tropsch reaction. Similarly, amines may also be produced by the conversion of reactant gas or gases, such as nitrogen, hydrogen, or hydrocarbon constituents.

  17. Nonhazardous solvent composition and method for cleaning metal surfaces

    DOEpatents

    Googin, J.M.; Simandl, R.F.; Thompson, L.M.

    1993-05-04

    A solvent composition for displacing greasy and oily contaminants as well as water and/or aqueous residue from metallic surfaces, especially surfaces of radioactive materials so that such surfaces can be wiped clean of the displaced contaminants, water and/or aqueous residue. The solvent composition consists essentially of a blend of nonpolar aliphatic hydrocarbon solvent having a minimum flash point of about 140 F and 2 to 25 volume percent of a polar solvent having a flash point sufficiently high so as to provide the solvent composition with a minimum flash point of at least 140 F. The solvent composition is nonhazardous so that when it is used to clean the surfaces of radioactive materials the waste in the form of paper or cloth wipes, lab coats and the like used in the cleaning operation is not considered to be mixed waste composed of a hazardous solvent and a radioactive material.

  18. Nonhazardous solvent composition and method for cleaning metal surfaces

    DOEpatents

    Googin, John M.; Simandl, Ronald F.; Thompson, Lisa M.

    1993-01-01

    A solvent composition for displacing greasy and oily contaminants as well as water and/or aqueous residue from metallic surfaces, especially surfaces of radioactive materials so that such surfaces can be wiped clean of the displaced contaminants, water and/or aqueous residue. The solvent composition consists essentially of a blend of nonpolar aliphatic hydrocarbon solvent having a minimum flash point of about 140.degree. F. and 2 to 25 volume percent of a polar solvent having a flash point sufficiently high so as to provide the solvent composition with a minimum flash point of at least 140.degree. F. The solvent composition is nonhazardous so that when it is used to clean the surfaces of radioactive materials the waste in the form of paper or cloth wipes, lab coats and the like used in the cleaning operation is not considered to be mixed waste composed of a hazardous solvent and a radioactive material.

  19. Mathematical model of the metal mould surface temperature optimization

    SciTech Connect

    Mlynek, Jaroslav Knobloch, Roman; Srb, Radek

    2015-11-30

    The article is focused on the problem of generating a uniform temperature field on the inner surface of shell metal moulds. Such moulds are used e.g. in the automotive industry for artificial leather production. To produce artificial leather with uniform surface structure and colour shade the temperature on the inner surface of the mould has to be as homogeneous as possible. The heating of the mould is realized by infrared heaters located above the outer mould surface. The conceived mathematical model allows us to optimize the locations of infrared heaters over the mould, so that approximately uniform heat radiation intensity is generated. A version of differential evolution algorithm programmed in Matlab development environment was created by the authors for the optimization process. For temperate calculations software system ANSYS was used. A practical example of optimization of heaters locations and calculation of the temperature of the mould is included at the end of the article.

  20. Immobilization of photosynthetic reaction centers on metal surfaces

    SciTech Connect

    Cotton, T.M.; Chumanov, G.; Gual, D.

    1993-12-31

    Membrane-bound proteins are ideal candidates for immobilization on surfaces because of their distinct hydrophobic and hydrophilic regions. Their interaction with a particular surface should depend upon its hydrophilicity. Variation of the surface properties is expected to result in changes in the orientation of an absorbed protein. In this study, two methods for immobilization of reaction centers from Rhodobacter sphaeroids on metal surfaces have been compared, including self-assembly or spontaneous adsorption and Langmuir-Blodgett transfer of monolayers from an air/water interface. The effect of the immobilization procedure on the structure of the protein complex has been determined from photochemical activity and optical measurements. The experimental variables which are critical for maintaining the structure and function of the protein in the adsorbed state will be discussed.

  1. Mathematical model of the metal mould surface temperature optimization

    NASA Astrophysics Data System (ADS)

    Mlynek, Jaroslav; Knobloch, Roman; Srb, Radek

    2015-11-01

    The article is focused on the problem of generating a uniform temperature field on the inner surface of shell metal moulds. Such moulds are used e.g. in the automotive industry for artificial leather production. To produce artificial leather with uniform surface structure and colour shade the temperature on the inner surface of the mould has to be as homogeneous as possible. The heating of the mould is realized by infrared heaters located above the outer mould surface. The conceived mathematical model allows us to optimize the locations of infrared heaters over the mould, so that approximately uniform heat radiation intensity is generated. A version of differential evolution algorithm programmed in Matlab development environment was created by the authors for the optimization process. For temperate calculations software system ANSYS was used. A practical example of optimization of heaters locations and calculation of the temperature of the mould is included at the end of the article.

  2. Carbide and carbonitride surface treatment method for refractory metals

    DOEpatents

    Meyer, Glenn A.; Schildbach, Marcus A.

    1996-01-01

    A carbide and carbonitride surface treatment method for refractory metals is provided, in steps including, heating a part formed of boron, chromium, hafnium, molybdenum, niobium, tantalum, titanium, tungsten or zirconium, or alloys thereof, in an evacuated chamber and then introducing reaction gases including nitrogen and hydrogen, either in elemental or water vapor form, which react with a source of elemental carbon to form carbon-containing gaseous reactants which then react with the metal part to form the desired surface layer. Apparatus for practicing the method is also provided, in the form of a carbide and carbonitride surface treatment system (10) including a reaction chamber (14), a source of elemental carbon (17), a heating subassembly (20) and a source of reaction gases (23). Alternative methods of providing the elemental carbon (17) and the reaction gases (23) are provided, as well as methods of supporting the metal part (12), evacuating the chamber (14) with a vacuum subassembly (18) and heating all of the components to the desired temperature.

  3. Designing an artificial Lieb lattice on a metal surface

    NASA Astrophysics Data System (ADS)

    Qiu, Wen-Xuan; Li, Shuai; Gao, Jin-Hua; Zhou, Yi; Zhang, Fu-Chun

    2016-12-01

    Recently, several experiments [K. K. Gomes et al., Nature (London) 483, 306 (2012), 10.1038/nature10941; S. Wang et al., Phys. Rev. Lett. 113, 196803 (2014), 10.1103/PhysRevLett.113.196803] have illustrated that metal surface electrons can be manipulated to form a two-dimensional (2D) lattice by depositing a designer molecule lattice on a metal surface. This offers a promising new technique to construct artificial 2D electron lattices. Here we theoretically propose a molecule lattice pattern to realize an artificial Lieb lattice on a metal surface, which shows a flat electronic band due to the lattice geometry. We show that the localization of electrons in the flat band may be understood from the viewpoint of electron interference, which may be probed by measuring the local density of states with scanning tunneling microscopy. Our proposal may be readily implemented in experiment and may offer an ideal solid state platform to investigate the novel flat band physics of the Lieb lattice.

  4. Online measurement system for the surface inclination of metal workpieces

    NASA Astrophysics Data System (ADS)

    Yin, Peng; Sun, Changku; Wang, Peng; Yang, Qian

    2013-12-01

    The online measurement of the metal surfaces' parameters plays an important role in many industrial fields. Because the surfaces of the machined metal pieces have the characteristics of strong reflection and high possibilities of scattered disturbing irradiation points, this paper designs an online measurement system based on the measurement principles of linear structured light to detect whether the parameters of the machined metal surfaces' height difference and inclination fulfill the compliance requirements, in which the grayscale gravity algorithm is applied to extract the sub-pixel coordinates of the center of laser, the least squares method is employed to fit the data and the Pauta criterion is utilized to remove the spurious points. The repeat accuracy of this system has been tested. The experimental results prove that the precision of inclination is 0.046° RMS under the speed of 40mm/sec, and the precision of height difference is 0.072mm RMS, which meets the design expectations. Hence, this system can be applied to online industrial detection of high speed and high precision.

  5. First Principles Simulations of Ice Nucleation at Metal Surfaces

    NASA Astrophysics Data System (ADS)

    Michaelides, Angelos

    2005-03-01

    Ice nucleation at solid surfaces is of relevance to countless scientific and technological processes. In particular the nucleation of ice nano-crystals on metal surfaces is often a key first step in cloud formation and corrosion [1]. Yet unfortunately this remains one of the most poorly understood natural phenomena; severely lacking in atomic level understanding. Here, we discuss detailed density functional theory studies aimed at putting our understanding of ice nucleation at metals on a much firmer footing. Specifically the properties of H2O hexamers - the smallest `building blocks' of ice - adsorbed on a number of close-packed transition metal surfaces have been examined. We find that the competing influences of substrate reactivity and hexamer-substrate epitaxial mismatch conspire to yield a rich variety of (novel) hexameric ice structures, some of which have been observed by recent scanning tunnelling microscopy experiments [2]. [1] H.R. Pruppacher and J.D. Klett, Microphysics of Clouds and Precipitation, (Kluwer, Dordrecht, 2003). [2] K. Morgenstern, et al., (To be published).

  6. Peptide immobilisation on porous silicon surface for metal ions detection

    NASA Astrophysics Data System (ADS)

    Sam, Sabrina S.; Chazalviel, Jean-Noël Jn; Gouget-Laemmel, Anne Chantal Ac; Ozanam, François F.; Etcheberry, Arnaud A.; Gabouze, Nour-Eddine N.

    2011-06-01

    In this work, a Glycyl-Histidyl-Glycyl-Histidine (GlyHisGlyHis) peptide is covalently anchored to the porous silicon PSi surface using a multi-step reaction scheme compatible with the mild conditions required for preserving the probe activity. In a first step, alkene precursors are grafted onto the hydrogenated PSi surface using the hydrosilylation route, allowing for the formation of a carboxyl-terminated monolayer which is activated by reaction with N-hydroxysuccinimide in the presence of a peptide-coupling carbodiimide N-ethyl- N'-(3-dimethylaminopropyl)-carbodiimide and subsequently reacted with the amino linker of the peptide to form a covalent amide bond. Infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy are used to investigate the different steps of functionalization. The property of peptides to form stable complexes with metal ions is exploited to achieve metal-ion recognition by the peptide-modified PSi-based biosensor. An electrochemical study of the GlyHisGlyHis-modified PSi electrode is achieved in the presence of copper ions. The recorded cyclic voltammograms show a quasi-irreversible process corresponding to the Cu(II)/Cu(I) couple. The kinetic factors (the heterogeneous rate constant and the transfer coefficient) and the stability constant of the complex formed on the porous silicon surface are determined. These results demonstrate the potential role of peptides grafted on porous silicon in developing strategies for simple and fast detection of metal ions in solution.

  7. Peptide immobilisation on porous silicon surface for metal ions detection.

    PubMed

    Sam, Sabrina S; Chazalviel, Jean-Noël Jn; Gouget-Laemmel, Anne Chantal Ac; Ozanam, François F; Etcheberry, Arnaud A; Gabouze, Nour-Eddine N

    2011-06-06

    In this work, a Glycyl-Histidyl-Glycyl-Histidine (GlyHisGlyHis) peptide is covalently anchored to the porous silicon PSi surface using a multi-step reaction scheme compatible with the mild conditions required for preserving the probe activity. In a first step, alkene precursors are grafted onto the hydrogenated PSi surface using the hydrosilylation route, allowing for the formation of a carboxyl-terminated monolayer which is activated by reaction with N-hydroxysuccinimide in the presence of a peptide-coupling carbodiimide N-ethyl-N'-(3-dimethylaminopropyl)-carbodiimide and subsequently reacted with the amino linker of the peptide to form a covalent amide bond. Infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy are used to investigate the different steps of functionalization.The property of peptides to form stable complexes with metal ions is exploited to achieve metal-ion recognition by the peptide-modified PSi-based biosensor. An electrochemical study of the GlyHisGlyHis-modified PSi electrode is achieved in the presence of copper ions. The recorded cyclic voltammograms show a quasi-irreversible process corresponding to the Cu(II)/Cu(I) couple. The kinetic factors (the heterogeneous rate constant and the transfer coefficient) and the stability constant of the complex formed on the porous silicon surface are determined. These results demonstrate the potential role of peptides grafted on porous silicon in developing strategies for simple and fast detection of metal ions in solution.

  8. Peptide immobilisation on porous silicon surface for metal ions detection

    PubMed Central

    2011-01-01

    In this work, a Glycyl-Histidyl-Glycyl-Histidine (GlyHisGlyHis) peptide is covalently anchored to the porous silicon PSi surface using a multi-step reaction scheme compatible with the mild conditions required for preserving the probe activity. In a first step, alkene precursors are grafted onto the hydrogenated PSi surface using the hydrosilylation route, allowing for the formation of a carboxyl-terminated monolayer which is activated by reaction with N-hydroxysuccinimide in the presence of a peptide-coupling carbodiimide N-ethyl-N'-(3-dimethylaminopropyl)-carbodiimide and subsequently reacted with the amino linker of the peptide to form a covalent amide bond. Infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy are used to investigate the different steps of functionalization. The property of peptides to form stable complexes with metal ions is exploited to achieve metal-ion recognition by the peptide-modified PSi-based biosensor. An electrochemical study of the GlyHisGlyHis-modified PSi electrode is achieved in the presence of copper ions. The recorded cyclic voltammograms show a quasi-irreversible process corresponding to the Cu(II)/Cu(I) couple. The kinetic factors (the heterogeneous rate constant and the transfer coefficient) and the stability constant of the complex formed on the porous silicon surface are determined. These results demonstrate the potential role of peptides grafted on porous silicon in developing strategies for simple and fast detection of metal ions in solution. PMID:21711937

  9. Binding of an adatom to a simple metal surface

    NASA Technical Reports Server (NTRS)

    Huntington, H. B.; Turk, L. A.; White, W. W., III

    1975-01-01

    The density functional formalism of Hohenberg and Kohn is used to investigate the energies, charge densities and forces which hold an adatom on the surface of a simple metal. The valence wavefunction of the adatom is fitted to the Herman-Skillman solutions at large distance and is simplified somewhat in the core region. The field of the ion is represented by the Ashcroft pseudopotential. For the metal the jellium model is used. Detailed calculations are carried out for a sodium adatom on a sodium surface. Simply juxtaposing adatom and surface gives a binding energy of about 1/3 eV. This value is approximately twice the surface energy per atom in the close-packed plane. Charge redistributions as determined variationally increase the binding energy by about 10%. The equilibrium distance for the adatom turns out to be 1.66 A from the surface, as compared with 1.52 A, the observed value for one-half the distance between the close-packed planes.

  10. Binding of an adatom to a simple metal surface

    NASA Technical Reports Server (NTRS)

    Huntington, H. B.; Turk, L. A.; White, W. W., III

    1975-01-01

    The density functional formalism of Hohenberg and Kohn is used to investigate the energies, charge densities and forces which hold an adatom on the surface of a simple metal. The valence wavefunction of the adatom is fitted to the Herman-Skillman solutions at large distance and is simplified somewhat in the core region. The field of the ion is represented by the Ashcroft pseudopotential. For the metal the jellium model is used. Detailed calculations are carried out for a sodium adatom on a sodium surface. Simply juxtaposing adatom and surface gives a binding energy of about 1/3 eV. This value is approximately twice the surface energy per atom in the close-packed plane. Charge redistributions as determined variationally increase the binding energy by about 10%. The equilibrium distance for the adatom turns out to be 1.66 A from the surface, as compared with 1.52 A, the observed value for one-half the distance between the close-packed planes.

  11. Atomic Diffusion and Molecular Self-Assembly on Metal Surfaces

    NASA Astrophysics Data System (ADS)

    Jewell, April D.

    The research described herein focuses on understanding and exploiting nanometer-scale surface phenomena with respect to surface reactivity and self-assembled systems. Using scanning tunneling miscroscopy, atoms and small molecules ( i.e., fewer than 30 atoms) adsorbed on metal surfaces were studied with the objective being to capture, understand, and manipulate the events occurring at the interface between gases and solid surfaces. The specific approach was to examine a variety of different but related chemical species in order to understand how chemical functionality affects the assembly behavior of technologically important species on metal surfaces. Using this systematic approach, in which, for example, only a single atom (or group of atoms) in the adsorbed species was varied, it was possible to uncover subtle differences in assembly behavior and overlayer stability. These differences are explained in terms of the chemical properties of the differing atom(s), which are based on well-established periodic trends and governed by electrostatics. Similar studies focusing on varying ligand functionality are also presented. Findings from this research add to our understanding of fundamental chemical interactions that govern assembly at the gas/solid interface. Importantly, the work here contributes to the establishment of heuristic rules that, in the future, could help predict assembly behavior. The impact of this research has the potential to transform our approach to sensor technology, heterogeneous catalysis, and other related fields.

  12. 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.

  13. Effect of composition and packing configuration on the dichroic optical properties of coinage metal nanorods.

    PubMed

    Cortie, M B; Xu, X; Ford, M J

    2006-08-14

    When nanorods of Au, Ag and some other elements are aligned with a preferred orientation with respect to light, their optical extinction characteristics become dependent on the polarization and angle of incidence of the light. This effect is explored here and it is shown that it could potentially be exploited to produce a 'colour-change coating'. However, particle-particle interactions are also likely to occur in such coatings, with red shifting of extinction spectra occurring for end-on-end configurations of monodisperse rods, and blue shifting for side-by-side configurations. Surprisingly, the particle-particle interactions are attenuated if they are between rods of differing aspect ratios, and this offers a useful new means of control of the optical properties of coatings of nanorods.

  14. Facile synthesis and improved optical activity in ZnO nanocrystallites doped with coinage metals

    NASA Astrophysics Data System (ADS)

    Sahu, Dojalisa; Panda, N. R.; Acharya, B. S.

    2015-06-01

    We report the growth of well-oriented rod and flower-like nanostructures of ZnO doped with copper, gold and silver synthesized by sonochemical method. The nanostructures were grown in a nutrient solution made of zinc nitrate (Zn(NO3)2 . 6H2O) and ammonia at low temperature with varying the dopant. XRD, TEM, UV-VIS, photoluminescence and FTIR spectra were recorded to study the crystallinity, microstructure and optical properties of the samples. XRD results show the formation of hexagonal wurtzite phase of ZnO with changing lattice parameters with doping. Both direct and indirect evidences were obtained from the XRD pattern confirming the incorporation of the dopant. Enhanced UV absorbance and PL emissions for ZnO has been observed and the role of Cu, Ag and Au in altering these properties has been investigated. Shift in UV band and evolution of new visible emission bands in the Pl spectra have been explained on the basis of incorporation of impurity occupying different states in the band gap of ZnO.

  15. Adatom surface diffusion of catalytic metals on the anatase TiO2(101) surface.

    PubMed

    Alghannam, Afnan; Muhich, Christopher L; Musgrave, Charles B

    2017-02-08

    Titanium oxide is often decorated with metal nano-particles and either serves as a catalyst support or enables photocatalytic activity. The activity of these systems degrades over time due to catalytic particle agglomeration and growth by Ostwald ripening where adatoms dissociate from metal particles, diffuse across the surface and add to other metal particles. In this work, we use density functional theory calculations to study the diffusion mechanisms of select group VIII and 1B late-transition metal adatoms commonly used in catalysis and photocatalysis (Au, Ag, Cu, Pt, Rh, Ni, Co and Fe) on the anatase TiO2(101) surface. All metal adatoms preferentially occupy the bridge site between two 2-fold-coordinated oxygen anions (O2c). Surface migration was investigated by calculating the minimum energy pathway from one bridge site to another along three pathways: two in the [010] direction along a row of surface O2c anions and one in the [101[combining macron

  16. Metal/metal-oxide interfaces: A surface science approach to the study of adhesion

    SciTech Connect

    Peden, C.H.F.; Kidd, K.B.; Shinn, N.D. )

    1991-05-01

    Metal-oxide/metal interfaces play an important role, for example, in the joining of an oxide ceramic to a metal for sealing applications. In order to probe the chemical and physical properties of such an interface, we have performed Auger electron spectroscopic (AES) and temperature programed desorption (TPD) experiments on a model system composed of very thin films of Cr, Fe, Ni, or Cu evaporated onto a very thin thermally grown oxide on a W single crystal. Monolayer films of Fe and Cr were found (by AES) to completely wet the oxide surface upon deposition, and were stable up to temperatures at which the films desorbed ({approx}1300 K). In contrast, monolayer Ni and Cu films formed three-dimensional islands exposing the oxidized W surface either upon annealing (Ni) or even upon room-temperature deposition (Cu). The relative interfacial interaction between the overlayer metal and the oxide, as assessed by TPD, increases in the series Cu{lt}Ni{lt}Fe{lt}Cr. This trend follows the heats of formation of the various oxides of these metals.

  17. Metal on metal surface replacement of the hip. Experience of the McMinn prothesis.

    PubMed

    McMinn, D; Treacy, R; Lin, K; Pynsent, P

    1996-08-01

    The historical failure of surface replacement has been due to the production of wear debris with subsequent bone resorption, loosening, and failure. To avoid these problems, a surface replacement using a metal on metal bearing allowing thin components and femoral design and instrumentation to avoid varus alignment has been designed. Two hundred thirty-five joints have been resurfaced with this prosthesis in almost 5 years. There have been no femoral neck fractures and no dislocations. There have been 4 designs differing in the method of fixation. In the press fit group, 6 of 70 hips had to be revised for aseptic loosening. In the cemented group, debonding of the cup occurred in 3 of 43 cases. Six patients had hydroxyapatite coated components and have had excellent clinical outcomes. The current design uses a peripherally expanded hydroxyapatite coated cup and a cemented metal head; 116 of this design have been implanted during a 19-month period with excellent outcome. Despite short followup the authors are hopeful that the combination of a polar metal on metal bearing with appropriate fixation will yield a method of preserving bone stock in the younger patient requiring arthroplasty.

  18. Surface modification by metal ion implantation forming metallic nanoparticles in an insulating matrix

    NASA Astrophysics Data System (ADS)

    Salvadori, M. C.; Teixeira, F. S.; Sgubin, L. G.; Cattani, M.; Brown, I. G.

    2014-08-01

    There is special interest in the incorporation of metallic nanoparticles in a surrounding dielectric matrix for obtaining composites with desirable characteristics such as for surface plasmon resonance, which can be used in photonics and sensing, and controlled surface electrical conductivity. We have investigated nanocomposites produced by metal ion implantation into insulating substrates, where the implanted metal self-assembles into nanoparticles. The nanoparticles nucleate near the maximum of the implantation depth profile (projected range), which can be estimated by computer simulation using the TRIDYN code. TRIDYN is a Monte Carlo simulation program based on the TRIM (Transport and Range of Ions in Matter) code that takes into account compositional changes in the substrate due to two factors: previously implanted dopant atoms, and sputtering of the substrate surface. Our study show that the nanoparticles form a bidimentional array buried a few nanometers below the substrate surface. We have studied Au/PMMA (polymethylmethacrylate), Pt/PMMA, Ti/alumina and Au/alumina systems. Transmission electron microscopy of the implanted samples show that metallic nanoparticles form in the insulating matrix. These nanocomposites have been characterized by measuring the resistivity of the composite layer as a function of the implantation dose. The experimental results are compared with a model based on percolation theory, in which electron transport through the composite is explained by conduction through a random resistor network formed by the metallic nanoparticles. Excellent agreement is found between the experimental results and the predictions of the theory. We conclude in that the conductivity process is due only to percolation (when the conducting elements are in geometric contact) and that the contribution from tunneling conduction is negligible.

  19. Anisotropic Second Harmonic Generation at Single Crystal Metal Surfaces.

    NASA Astrophysics Data System (ADS)

    Kexiang, He.

    The work in this thesis comprises a set of experiments designed to study the anisotropic spatial dependence of second harmonic generation (SHG) from the surface of single crystal metals. The anisotropic dependence of reflected SHG from Al_2O_3 Al(111) interface was studied. The isotropic dependence of the SHG signal is used to probe the structural symmetry of the Al_2O_3Al(111) interface. For P- and S-polarized laser light incident at a fixed angle of 45^circ, the intensities of S- and P-polarized components of SHG signal were measured as a function of rotation angle during rotation of the surface about its normal. Anisotropic SHG studies were also performed on high Miller index surface of Al(331) and on a Al surface cut at 22.5^ circ with respect to the Al(111) surface. For the Al(331) surface, the anisotropic dependence of the SHG signal was measured for both the S- and P-polarized signals under both S- and P-polarized laser excitation. The anisotropy of the SHG from Al(331) were fit with theory using the assumption that symmetry is retained for this surface at the metal oxide-metal interface. Existing theory is used to derive the theoretical expressions predicting the anisotropic dependence of SHG from Al(331). The SHG probe was also used to follow pulsed laser annealing (PLA) of the Al_2O_3/Al(111) interface from on a chemically polished Al(111) surface. Using P-polarized pump laser light, the P-polarized SHG signal exhibits three equally spaced, equal intensity maxima during a single complete rotation of Al_2O _3/Al(111) interface about the interface normal. Annealing of the interface is found to occur when the P-polarized 1064nm pump laser light has an incident peak power of 11 times 10 ^6W/cm^2 per pulse. The intensity of the P-polarized 532nm SHG signal generated in reflection from this annealed interface exhibits a reduced anisotropic component in the SHG signal. Measurements of the anisotropic SHG signal from ionized beam deposited Al thin-films on Si(111

  20. Ab initio calculations of generalized-stacking-fault energy surfaces and surface energies for FCC metals

    NASA Astrophysics Data System (ADS)

    Wu, Xiao-Zhi; Wang, Rui; Wang, Shao-Feng; Wei, Qun-Yi

    2010-08-01

    The ab initio calculations have been used to study the generalized-stacking-fault energy (GSFE) surfaces and surface energies for the closed-packed (1 1 1) plane in FCC metals Cu, Ag, Au, Ni, Al, Rh, Ir, Pd, Pt, and Pb. The GSFE curves along <112> (1 1 1) direction and <110> (1 1 1) direction, and surface energies have been calculated from first principles. Based on the translational symmetry of the GSFE surfaces, the fitted expressions have been obtained from the Fourier series. Our results of the GSFEs and surface energies agree better with experimental results. The metals Al, Pd, and Pt have low γ/γI value, so full dislocation will be observed easily; while Cu, Ag, Au, and Ni have large γ/γI value, so it is preferred to create partial dislocation. From the calculations of surface energies, it is confirmed that the VIII column elements Ni, Rh, Ir, Pd, and Pt have higher surface energies than other metals.

  1. Metals in the surface sediments of Istanbul Strait (Turkey).

    PubMed

    Okay, Oya S; Pekey, Hakan; Morkoc, Enis; Basak, Serden; Baykal, Berna

    2008-12-01

    Surface sediments from 17 stations in the Istanbul Strait and Marmara Sea were collected and analysed for major and trace elements by wavelength-dispersive X-ray fluorescence spectrometry (WDXRF). Metal concentrations in surface sediments varied from 1.3 to 7.2 % for Al, 4.8 to 18 mg kg(- 1) for As, 119 to 599 mg kg(- 1) for Ba, below detection limit (bdl) to 6.6 mg kg(- 1) for Cd, 18 to 222 mg kg(- 1) for Cr, 7.6 to 180 mg kg(- 1) for Cu, 1.0 to 5.5 % for Fe (10 000 to 55 000 mg kg(- 1)), 171 to 718 mg kg(- 1)for Mn, 3.3 to 64 mg kg(- 1) for Ni, 4.5 to 461 mg kg(- 1) for Pb, 1.3 to 68 mg kg(- 1) for Sn, 19 to 170 mg kg(- 1) for V and 16 to 859 mg kg(- 1) for Zn. Three tools have been applied in order to evaluate metal pollution in the sediments; Sediment quality guidelines (SQGs), enrichment factors (EFs) and geoaccumulation index (I(geo)). SQGs values indicate that Pb and Ni are the most likely contaminants to cause adverse biological effects. On the other hand, both metal enrichment factors and geoaccumulation index show that As, Zn, Pb and Cd contaminations exist in the entire study area and contamination of other metals is also present in some sites depending on the sources. Factor analysis (FA) receptor modelling technique was applied to investigate the sources affecting surface sediment samples at the Istanbul Strait.

  2. Friction, Wear, and Surface Damage of Metals as Affected by Solid Surface Films

    NASA Technical Reports Server (NTRS)

    Bisson, Edmond E; Johnson, Robert L; Swikert, Max A; Godfrey, Douglas

    1956-01-01

    As predicted by friction theory, experiments showed that friction and surface damage of metals can be reduced by solid surface films. The ability of materials to form surface films that prevent welding was a very important factor in wear of dry and boundary lubricated surfaces. Films of graphitic carbon on cast irons, nio on nickel alloys, and feo and fe sub 3 o sub 4 on ferrous materials were found to be beneficial. Abrasive films such as fe sub 2 o sub 3 or moo sub 3 were definitely detrimental. It appears that the importance of oxide films to friction and wear processes has not been fully appreciated.

  3. Metal ion implantation for large scale surface modification

    SciTech Connect

    Brown, I.G.

    1992-10-01

    Intense energetic beams of metal ions can be produced by using a metal vapor vacuum arc as the plasma discharge from which the ion beam is formed. We have developed a number of ion sources of this kind and have built a metal ion implantation facility which can produce repetitively pulsed ion beams with mean ion energy up to several hundred key, pulsed beam current of more than an ampere, and time averaged current of several tens of milliamperes delivered onto a downstream target. We've also done some preliminary work on scaling up this technology to very large size. For example, a 50-cm diameter (2000 cm[sup 2]) set of beam formation electrodes was used to produce a pulsed titanium beam with ion current over 7 amperes at a mean ion energy of 100 key. Separately, a dc embodiment has been used to produce a dc titanium ion beam with current over 600 mA, power supply limited in this work, and up to 6 amperes of dc plasma ion current was maintained for over an hour. In a related program we've developed a plasma immersion method for applying thin metallic and compound films in which the added species is atomically mixed to the substrate. By adding a gas flow to the process, well-bonded compound films can also be formed; metallic films and multilayers as well as oxides and nitrides with mixed transition zones some hundreds of angstroms thick have been synthesized. Here we outline these parallel metal-plasma-based research programs and describe the hardware that we've developed and some of the surface modification research that we've done with it.

  4. Metal oxide surfaces for enhanced colorimetric response in bioassays.

    PubMed

    Bonyi, Enock; Kukoyi, Zeenat; Daodu, Oluseyi; Boone-Kukoyi, Zainab; Coskun, Sahin; Unalan, Husnu Emrah; Aslan, Kadir

    2017-06-01

    Physical stability of metal nanoparticle films on planar surfaces can be increased by employing surface modification techniques and/or type of metal nanoparticles. Subsequently, the enzymatic response of colorimetric bioassays can be increased for improved dynamic range for the detection of biomolecules. Using a model bioassay b-BSA, three planar platforms (1) poly (methyl methacrylate) (PMMA) with silver thin films (STFs), (2) silver nanowires (Ag NWs) on paper and (3) indium tin oxide (ITO) on polyethylene terephthalate (PET) were evaluated to investigate the extent of increase in the colorimetric signal. Bioassays for b-BSA and Ki-67 antigen (a real-life bioassay) in buffer were performed using microwave heating (total assay time is 25-30min) and at room temperature (a control experiment, total assay time is 3h). Model bioassays showed that STFs were removed from the surface during washing steps and the extent of ITO remained unchanged. The lowest level of detection (LLOD) for b-BSA bioassays were: 10(-10)M for 10nm STFs on PMMA and Ag NWs on paper and 10(-11)M for ITO. Bioassays for Ki-67 antigen yielded a LLOD of <10(-9)M on ITO platforms, while STFs platforms were deemed unusable due to significant loss of STFs from the surfaces. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. Quantum mechanics of effective potential at a metal surface

    NASA Astrophysics Data System (ADS)

    Solomatin, Alexander

    In this thesis we study the nonuniform electron density system at a metal-vacuum interface via the corresponding local effective potential confining the electrons, the metal being represented by the jellium and structureless pseudopotential models. The study is performed within conventional Kohn-Sham (KS) density-functional theory and its recently derived quantum-mechanical interpretation. In the latter, properties are determined in terms of the separate electron correlations due to the Pauli exclusion principle, Coulomb repulsion and the correlation contribution to the kinetc energy. We have derived the exact analytical structure, valid for self-consistent orbitals, of the KS theory exchange potential in the classically forbidden region. This structure is image-potential-like of the form -alphasb{KS,x}(beta)chi where the parameter betasp2 is the ratio of the surface barrier height to the metal Fermi energy. For a Wigner-Seitz radius of rsb{s} = 4.1, which is approximately that for which jellium metal is stable, the decay coefficient is precisely 1/4. Over the metallic range of densities rsb{s} = 2-6, the coefficient ranges from 0.195 to 0.274. Thus, if the asymptotic structure of the KS exchange-correlation potential is the image potential, then this structure is due principally to KS exchange effects, the KS correlation contribution being an order of magnitude smaller. These results, then lead to the concept of an 'image' charge localized to the surface region for asymptotic positions of the electron. We have further derived the exact analytical structure in the vacuum of the Slater exchange potential, and of the Pauli-correlation and correlation-kinetic components of the KS exchange potential. These structures are all image-potential-like, decaying respectively as -alphasb{S}(beta)chi,\\ -alphasb{W}(beta)chi and alphasbsp{tsb{c}}{(1)}(beta)/chi. The Pauli-correlation component constitutes the major fraction of the KS exchange potential asymptotically, but there

  6. Modeling surface plasmon-polariton gain in planar metallic structures.

    PubMed

    De Leon, Israel; Berini, Pierre

    2009-10-26

    Amplification of the single-interface and long-range surface plasmon-polariton modes is studied in planar metallic structures incorporating gain media formed by Rhodamine 6G dye molecules in solution. We employ a theoretical model that accounts for the nonuniformity of the gain medium close to the metal surface due to position-dependent dipole lifetime and pump irradiance. The results of this model are used as a baseline for a comparative study against two simplified models: one neglects the position-dependent dipole lifetime while the other assumes a uniform gain medium. The discrepancies between the models are explained in terms of the mode overlap with the gain distribution near the metal. For the cases under analysis, the simplified models estimate the required pump irradiance with deviation factors that vary from 1.45 at the lossless conditions to 8 for gains near saturation. The relevance of describing properly the amount o gain interacting with the SPP mode and the role played by the dipole quantum efficiency are discussed.

  7. Distinctive Damage Patterns on THA Metal Bearing Surfaces: Case Studies

    PubMed Central

    Heiner, Anneliese D; Tikekar, Nishant M; Kruger, Karen M; Lannutti, John J; Brown, Thomas D

    2014-01-01

    Retrieval analysis of total joint arthroplasty components has primarily focused on assessing wear or other damage to polyethylene components. As damage to the opposing bearing surface can accelerate polyethylene wear and damage, and especially with the use of hard-on-hard articulations, retrieval analysis benefits from incorporating evaluation of hard bearing surfaces as well. The purpose of this study is to report six case studies of metal bearing surfaces with distinctive damage patterns, to interpret them in the context of adverse events plausibly responsible for their creation, and to suggest their likely clinical or scientific significance. The specific damage patterns reported here are 1) extensive scraping, 2) circumferential discoloration, 3) a long chain of periodic micro-indentations, 4) pitting with deposits, 5) scratches with small-radius directional changes, and 6) indentation with scraping. PMID:25328465

  8. Surfactant-Modified Diffusion on Transition-Metal Surfaces

    SciTech Connect

    FEIBELMAN,PETER J.; KELLOGG,GARY LEE

    1999-12-01

    Wanting to convert surface impurities from a nuisance to a systematically applicable nano-fabrication tool, we have sought to understand how such impurities affect self-diffusion on transition-metal surfaces. Our field-ion microscope experiments reveal that in the presence of surface hydrogen, self-diffusion on Rh(100) is promoted, while on Pt(100), not only is it inhibited, but its mechanism changes. First-principles calculations aimed at learning how oxygen fosters perfect layerwise growth on a growing Pt(111) crystal contradict the idea in the literature that it does so by directly promoting transport over Pt island boundaries. The discovery that its real effect is to burn off adventitious adsorbed carbon monoxide demonstrates the predictive value of state-of-the-art calculation methods.

  9. First principles investigation of heterogeneous catalysis on metal oxide surfaces

    NASA Astrophysics Data System (ADS)

    Ghoussoub, Mireille

    Metal oxides possess unique electronic and structural properties that render them highly favourable for applications in heterogeneous catalysis. In this study, computational atomistic modelling based on Density Functional Theory was used to investigate the reduction of carbon dioxide over hydroxylated indium oxide nanoparticles, as well at the activation of methane over oxygen-covered bimetallic surfaces. The first study employed metadynamics-biased ab initio molecular dynamics to obtain the free energy surface of the various reaction steps at finite temperature. In the second study, the nudged elastic band method was used to probe the C-H activation mechanisms for different surface configurations. In both cases, activation energies, reaction energies, transition state structures, and charge analysis results are used to explain the underlying mechanistic pathways.

  10. Adhesion of metals to a clean iron surface studied with LEED and Auger emission spectroscopy.

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.

    1972-01-01

    Discussion of the results of adhesion experiments conducted with various metals contacting a clean iron surface. The metals included gold, silver, nickel, platinum, lead, tantalum, aluminum, and cobalt. Some of the metals were examined with oxygen present on their surface as well as in the clean state. The results indicate that, with the various metals contacting iron, the cohesively weaker will adhere and transfer to the cohesively stronger. The chemical activity of the metal also influenced the adhesive forces measured. With oxygen present on the metal surface, the adhesive forces measured could be correlated with the binding energy of the metal to oxygen.

  11. Adhesion of metals to a clean iron surface studied with LEED and Auger emission spectroscopy.

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.

    1972-01-01

    Discussion of the results of adhesion experiments conducted with various metals contacting a clean iron surface. The metals included gold, silver, nickel, platinum, lead, tantalum, aluminum, and cobalt. Some of the metals were examined with oxygen present on their surface as well as in the clean state. The results indicate that, with the various metals contacting iron, the cohesively weaker will adhere and transfer to the cohesively stronger. The chemical activity of the metal also influenced the adhesive forces measured. With oxygen present on the metal surface, the adhesive forces measured could be correlated with the binding energy of the metal to oxygen.

  12. Influence of Surface Morphology on the Antimicrobial Effect of Transition Metal Oxides in Polymer Surface.

    PubMed

    Oh, Yoo Jin; Hubauer-Brenner, Michael; Hinterdorfer, Peter

    2015-10-01

    In this study, the physical properties of transition metal oxide surfaces were examined using scanning probe microscopic (SPM) techniques for elucidating the antimicrobial activity of molybdenum trioxide (MoO3), tungsten trioxide (WO3), and zinc oxide (ZnO) embedded into the polymers thermoplastic polyurethane (TPU) and polypropylene (PP). We utilized atomic force microscopy (AFM) in the contact imaging mode and its derivative single-pass Kelvin probe force microscopy for investigating samples that were presumably identical in their compositions, but showed different antimicrobial activity in bacterial adhesion tests. Our results revealed that surfaces with larger roughness and higher surface potential variation showed stronger antimicrobial activities compared to smoother and homogeneously charge-distributed surfaces. In addition, capacitance gradient (dC/dZ) measurements were performed to elucidate the antimicrobial activity arising from the different dielectric behavior of the transition metal oxides in this heterogeneous polymer surface. We found that the nano-scale exposure of transition metal oxides on polymer surfaces provided strong antimicrobial effects. Applications arising from our studies will be useful for public and healthcare environments.

  13. Self-assembly of metal nanostructures on binary alloy surfaces.

    PubMed

    Duguet, T; Han, Yong; Yuen, Chad; Jing, Dapeng; Unal, Barış; Evans, J W; Thiel, P A

    2011-01-18

    Deposition of metals on binary alloy surfaces offers new possibilities for guiding the formation of functional metal nanostructures. This idea is explored with scanning tunneling microscopy studies and atomistic-level analysis and modeling of nonequilibrium island formation. For Au/NiAl(110), complex monolayer structures are found and compared with the simple fcc(110) bilayer structure recently observed for Ag/NiAl(110). We also consider a more complex codeposition system, (Ni + Al)/NiAl(110), which offers the opportunity for fundamental studies of self-growth of alloys including deviations for equilibrium ordering. A general multisite lattice-gas model framework enables analysis of structure selection and morphological evolution in these systems.

  14. Self-assembly of metal nanostructures on binary alloy surfaces

    PubMed Central

    Duguet, T.; Han, Yong; Yuen, Chad; Jing, Dapeng; Ünal, Barış; Evans, J. W.; Thiel, P. A.

    2011-01-01

    Deposition of metals on binary alloy surfaces offers new possibilities for guiding the formation of functional metal nanostructures. This idea is explored with scanning tunneling microscopy studies and atomistic-level analysis and modeling of nonequilibrium island formation. For Au/NiAl(110), complex monolayer structures are found and compared with the simple fcc(110) bilayer structure recently observed for Ag/NiAl(110). We also consider a more complex codeposition system, (Ni + Al)/NiAl(110), which offers the opportunity for fundamental studies of self-growth of alloys including deviations for equilibrium ordering. A general multisite lattice-gas model framework enables analysis of structure selection and morphological evolution in these systems. PMID:21097706

  15. Surface Plasmon Resonance Evaluation of Colloidal Metal Aerogel Filters

    NASA Technical Reports Server (NTRS)

    Smith, David D.; Sibille, Laurent; Cronise, Raymond J.; Noever, David A.

    1997-01-01

    We have fabricated aerogels containing gold, silver, and platinum nanoparticles for gas catalysis applications. By applying the concept of an average or effective dielectric constant to the heterogeneous interlayer surrounding each particle, we extend the technique of immersion spectroscopy to porous or heterogeneous media. Specifically, we apply the predominant effective medium theories for the determination of the average fractional composition of each component in this inhomogeneous layer. Hence, the surface area of metal available for catalytic gas reaction is determined. The technique is satisfactory for statistically random metal particle distributions but needs further modification for aggregated or surfactant modified systems. Additionally, the kinetics suggest that collective particle interactions in coagulated clusters are perturbed during silica gelation resulting in a change in the aggregate geometry.

  16. Infrared transparent frequency selective surface based on metallic meshes

    SciTech Connect

    Yu, Miao; Xu, Nianxi; Liu, Hai; Gao, Jinsong

    2014-02-15

    This paper presents an infrared transparent frequency selective surface (ITFSS) based on metallic meshes. In this ITFSS structure, periodic cross-slot units are integrated on square metallic meshes empowered by coating and UV-lithography. A matching condition is proposed to avoid the distortion of units. Experimental results show that this ITFSS possesses a good transmittance of 80% in the infrared band of 3–5 μm, and also a stable band-pass behavior at the resonance frequency of 36.4 GHz with transmittance of −0.56 dB. Theoretical simulations about the ITFSS diffractive characteristics and frequency responses are also investigated. The novel ITFSS will attract renewed interest and be exploited for applications in various fields.

  17. Chemical and spectroscopic studies of metal oxide surfaces

    SciTech Connect

    Goodman, D.W.

    1996-05-01

    Thin oxide films (e.g., 5{endash}10 nm of SiO{sub 2}, Al{sub 2}O{sub 3}, NiO, MgO) supported on a refractory metal substrate (e.g., Mo, W, Ta, Re) have been prepared by deposition of the oxide metal precursor in a background of oxygen. The thin-film nature of these samples facilitates investigation by an array of surface techniques, many of which cannot be effectively utilized on the corresponding bulk oxide. The structural, electronic, and chemical properties of these films have been studied with temperature programmed desorption, Auger electron spectroscopy, X-ray photoelectron spectroscopy, ion scattering spectroscopy, high resolution electron energy loss spectroscopy, and infrared reflection absorption spectroscopy. The results of these studies demonstrate the viability of using thin oxide films as models for the corresponding bulk oxide. {copyright} {ital 1996 American Vacuum Society}

  18. Surface Plasmon Resonance Evaluation of Colloidal Metal Aerogel Filters

    NASA Technical Reports Server (NTRS)

    Smith, David D.; Sibille, Laurent; Cronise, Raymond J.; Noever, David A.

    1997-01-01

    We have fabricated aerogels containing gold, silver, and platinum nanoparticles for gas catalysis applications. By applying the concept of an average or effective dielectric constant to the heterogeneous interlayer surrounding each particle, we extend the technique of immersion spectroscopy to porous or heterogeneous media. Specifically, we apply the predominant effective medium theories for the determination of the average fractional composition of each component in this inhomogeneous layer. Hence, the surface area of metal available for catalytic gas reaction is determined. The technique is satisfactory for statistically random metal particle distributions but needs further modification for aggregated or surfactant modified systems. Additionally, the kinetics suggest that collective particle interactions in coagulated clusters are perturbed during silica gelation resulting in a change in the aggregate geometry.

  19. Casimir Interaction between Plane and Spherical Metallic Surfaces

    SciTech Connect

    Canaguier-Durand, Antoine; Cavero-Pelaez, Ines; Lambrecht, Astrid; Reynaud, Serge; Maia Neto, Paulo A.

    2009-06-12

    We give an exact series expansion of the Casimir force between plane and spherical metallic surfaces in the nontrivial situation where the sphere radius R, the plane-sphere distance L and the plasma wavelength {lambda}{sub P} have arbitrary relative values. We then present numerical evaluation of this expansion for not too small values of L/R. For metallic nanospheres where R, L and {lambda}{sub P} have comparable values, we interpret our results in terms of a correlation between the effects of geometry beyond the proximity force approximation and of finite reflectivity due to material properties. We also discuss the interest of our results for the current Casimir experiments which are performed with spheres of large radius R>>L.

  20. Direct versus hydrogen assisted CO dissociation on metal surfaces

    NASA Astrophysics Data System (ADS)

    Alfonso, Dominic

    2012-02-01

    We present investigations of the formation of precursor hydrocarbon species relevant to production of liquid hydrocarbons on low index surfaces of various important noble and transition metals. The formation could occur via the so-called carbide mechanism where direct CO dissociation takes place, followed by stepwise hydrogenation of C yielding CHx species. Formation of precursor CHx species could also potentially take place through hydrogenated CO intermediates. First-principles calculations of energetics and barriers of CO conversion to hydrocarbons species were performed using plane-wave periodic density functional theory. Our calculations indicate that the two pathways are generally competitive on transition metals. A microkinetic model, with input thermodynamics and kinetic parameters estimated from electronic structure calculations, has been developed. The two pathways will be further examined using microkinetic approach to determine whether the aforementioned finding holds at realistic conditions.

  1. Reliable simulation of metal surface penetration by lightning continuing currents

    SciTech Connect

    Zischank, W.; Drumm, F.; Fisher, R.J.; Schnetzer, G.H.; Morris, M.E.

    1995-08-01

    Of specific interest to Sandia National Laboratories is the assessment and reduction of the potential safety threat posed by the penetration of metallic casings of munitions due to the direct attachment of lightning strikes. A program with the ultimate aim of quantifying the fidelity of laboratory test techniques used to simulate the penetration of metallic surfaces by lightning continuing currents has been undertaken. Descriptions of the program methodology, dominant factors found to influence test results, and data obtained so far are given. Based on considerations of fundamental arc phenomenology and on the acquired experimental data, a standard test configuration has been established, which has been demonstrated at two independent laboratories to produce consistent results that are generally corroborative of techniques suggested elsewhere in the lightning literature.

  2. Assembly of Ferrocene Molecules on Metal Surfaces Revisited.

    PubMed

    Ormaza, Maider; Abufager, Paula; Bachellier, Nicolas; Robles, Roberto; Verot, Martin; Le Bahers, Tangui; Bocquet, Marie-Laure; Lorente, Nicolas; Limot, Laurent

    2015-02-05

    Metallocene (MCp2) wires have recently attracted considerable interest in relation to molecular spintronics due to predictions concerning their half-metallic nature. This exciting prospect is however hampered by the little and often-contradictory knowledge we have concerning the metallocene self-assembly and interaction with a metal. Here, we elucidate these aspects by focusing on the adsorption of ferrocene on Cu(111) and Cu(100). Combining low-temperature scanning tunneling microscopy and density functional theory calculations, we demonstrate that the two-dimensional molecular arrangement consists of vertical- and horizontal-lying molecules. The noncovalent T-shaped interactions between Cp rings of vertical and horizontal molecules are essential for the stability of the physisorbed molecular layer. These results provide a fresh insight into ferrocene adsorption on surfaces and may serve as an archetypal reference for future work with this important variety of organometallic molecules.

  3. Catalysis and surface properties of liquid metals and alloys

    SciTech Connect

    Ogino, Y.

    1987-01-01

    This book presents a historical review of the subject in order to clarify its own role in advancing the study of heterogenous catalysis. In addition, this authoritative volume; discusses the catalytic properties of liquid metals and alloys, giving a useful, schematic account of various experimental techniques; examines the mechanism of catalysis at the atomic and particle levels, defining the structures of liquid metals; covers a variety of reactions, including dehydrogenation, hydrogen transfer, coal liquefaction, and other, suggesting practical uses and additional areas for investigation; addresses basic and microscopic aspects of catalysis, exploring such advanced topics as kinetics and stereochemistry as well as optical properties and surface transition zones; and provides examples of applications, illustrating fundamental research with specific technologies that extend the range of future research possibilities.

  4. Surface oxidation of metals by oxygen ion bombardment

    NASA Astrophysics Data System (ADS)

    Alov, Nikolai V.

    2007-03-01

    Surface oxidation of molybdenum, tungsten, niobium and tantalum by low-energy oxygen ion beams is investigated using X-ray photoelectron spectroscopy (XPS). Oxygen ion bombardment of molybdenum and tungsten surfaces leads to the formation of thin oxide films containing metals in oxidation states 4+, 5+ and 6+. At the initial stage of irradiation, rapid surface oxidation of molybdenum and tungsten was observed. At higher fluences the oxidation reaches saturation and the surface composition remains almost unchanged with increasing fluence. Oxygen ion bombardment of niobium and tantalum surfaces leads to the formation of thin oxide films containing niobium and tantalum in oxidation states 2+, 4+ and 5+. At the initial stage of irradiation, again rapid surface oxidation of niobium and tantalum was observed. At higher fluences the population of Nb2+ and Nb4+, Ta2+ and Ta4+ reaches a maximum and then begins to decrease. The population of Nb5+ and Ta5+ continues to increase and finally the entire oxide films consists of only Nb5+ and Ta5+, respectively.

  5. Surface arthroplasty for osteonecrosis of the hip: hemiresurfacing versus metal-on-metal hybrid resurfacing.

    PubMed

    Beaulé, Paul E; Amstutz, Harlan C; Le Duff, Michel; Dorey, Frederic

    2004-12-01

    Eighty-four hips with Ficat stage III and IV osteonecrosis were treated: 56 with metal-on-metal surface arthroplasty (MMSA) and 28 with hemi-surface arthroplasty (HSA). Average follow-up was 4.9 years. UCLA hip scores were significantly better for MMSA versus HSA for function and activity as well as Harris Hip scores and physical component of the SF-12 scores. In the MMSA group, 2 hips were revised to total hip arthroplasty for femoral loosening, and 5 hips had adverse radiological changes. In the HSA group, 4 hips were revised (1 sepsis and 3 for pain). There was no evidence of any femoral loosening or neck narrowing in the HSA group. Although the functional clinical outcome of MMSA is superior to HSA, long-term follow up of MMSA will determine the reliability of the femoral fixation.

  6. Molecular design of the microbial cell surface toward the recovery of metal ions.

    PubMed

    Kuroda, Kouichi; Ueda, Mitsuyoshi

    2011-06-01

    The genetic engineering of microorganisms to adsorb metal ions is an attractive method to facilitate the environmental cleanup of metal pollution and to enrich the recovery of metal ions such as rare metal ions. For the recovery of metal ions by microorganisms, cell surface design is an effective strategy for the molecular breeding of bioadsorbents as an alternative to intracellular accumulation. The cell surface display of known metal-binding proteins/peptides and the molecular design of novel metal-binding proteins/peptides have been performed using a cell surface engineering approach. The adsorption of specific metal ions is the important challenge for the practical recovery of metal ions. In this paper, we discuss the recent progress in surface-engineered bioadsorbents for the recovery of metal ions. Copyright © 2011 Elsevier Ltd. All rights reserved.

  7. A Safe Solution to Dopant Gas Desorption from Metal Surfaces

    NASA Astrophysics Data System (ADS)

    Nakanoya, Tsutomu; Egami, Maki

    2006-11-01

    TOXICAPTURE™ is used to further minimize trace toxic dopant gas inside cylinder valve outlets, which, over time, may desorb from metal surfaces. When outlet caps or connections to ion source gas cylinders are disconnected in order to perform installations or bottle changes, there always is some risk that toxic fumes resulting from desorption of the metal surface in contact with dopant gas are released in air and inhaled by the operator. TOXICAPTURE™ is a simple and easy solution to reduce this risk that may damage human health or may pollute clean room environment. TOXICAPTURE™ will react with the poison gas vapor to form nontoxic and solid material through irreversible chemical reactions. TOXICAPTURE™ prevents contamination and corrosion on gas contact surfaces of gas pipings, pressure regulators, pneumatic valves, mass flow controllers, and other parts in a gas box. TOXICAPTURE™ is highly effective in shortening the time to achieve high vacuum and in extending the lifetime of devices in the gas box. In this paper, we introduce the structure, functions, reactivity, applications, and effectivity of TOXICAPTURE™.

  8. Noble gases on metal surfaces: Insights on adsorption site preference

    SciTech Connect

    Chen, De-Li; Al-Saidi, W. A.; Johnson, J. Karl

    2011-12-19

    We use a nonlocal van der Waals density functional (vdW-DF) approach to reexamine the problem of why noble gases are experimentally observed to adsorb on low-coordination atop sites rather than on high-coordination hollow sites for several different metal surfaces. Previous calculations using density functional theory (DFT) within the local density approximation (LDA) ascribed the site preference to reduced Pauli repulsion at atop sites, largely due to reduced exchange repulsion within LDA-DFT. In contrast, our vdW-DF calculations show that site preference is not due to differences in the exchange repulsion at all, but rather the result of a delicate balance between the electrostatic and kinetic energies; surprisingly, exchange-correlation energies play a negligible role in determining site preference. In contrast to previous calculations, we find that experimental results cannot be explained in terms of binding energy differences between atop and hollow sites. Instead, we show that the hollow sites are transition states rather than minima on the two-dimensional potential energy surface, and therefore not likely to be observed in experiments. This phenomenon is quite general, holding for close-packed and non-close-packed metal surfaces. We show that inclusion of nonlocal vdW interactions is crucial for obtaining results in quantitative agreement with experiments for adsorption energies, equilibrium distances, and vibrational energies.

  9. Covalent immobilization of liposomes on plasma functionalized metallic surfaces.

    PubMed

    Mourtas, S; Kastellorizios, M; Klepetsanis, P; Farsari, E; Amanatides, E; Mataras, D; Pistillo, B R; Favia, P; Sardella, E; d'Agostino, R; Antimisiaris, S G

    2011-05-01

    A method was developed to functionalize biomedical metals with liposomes. The novelty of the method includes the plasma-functionalization of the metal surface with proper chemical groups to be used as anchor sites for the covalent immobilization of the liposomes. Stainless steel (SS-316) disks were processed in radiofrequency glow discharges fed with vapors of acrylic acid to coat them with thin adherent films characterized by surface carboxylic groups, where liposomes were covalently bound through the formation of amide bonds. For this, liposomes decorated with polyethylene glycol molecules bearing terminal amine-groups were prepared. After ensuring that the liposomes remain intact, under the conditions applying for immobilization; different attachment conditions were evaluated (incubation time, concentration of liposome dispersion) for optimization of the technique. Immobilization of calcein-entrapping liposomes was evaluated by monitoring the percent of calcein attached on the surfaces. Best results were obtained when liposome dispersions with 5mg/ml (liposomal lipid) concentration were incubated on each disk for 24h at 37°C. The method is proposed for developing drug-eluting biomedical materials or devices by using liposomes that have appropriate membrane compositions and are loaded with drugs or other bioactive agents.

  10. Surface Characterization of Alkali and Alkaline Earth Metals on Single Crystal Refractory Metals

    NASA Astrophysics Data System (ADS)

    Magera, Gerald Glenn

    1995-11-01

    The experiments were conducted on the clean surfaces of W(110), Mo(110) and Nb(110) under ultrahigh vacuum conditions using techniques of line-of-sight thermal desorption mass spectrometry, Auger electron spectroscopy and retarding potential work function measurement. The clean work functions for W(110), Mo(110) and Nb(110) were found to be 5.38 eV, 5.08 eV and 4.62 eV, respectively. The behavior of the work function was characteristic of alkali and alkaline earth metal adsorption onto refractory metal surfaces with the minimum work function for the three surfaces of approximately 1.50 eV for cesium and 2.20 eV for barium. The results of the change in work function versus adsorption of cesium onto the bariated surfaces of W(110), Mo(110) and Nb(110) were similar. The energies of desorption for the different binding states were calculated for the various adsorbate-metal systems using first order desorption kinetics, that is, the adsorbates desorb at a rate linearly dependent on coverage. The desorption spectra for cesium from the various metal surfaces showed three distinct desorption sites, while barium had a more continuous decrease in activation energy of desorption up to a monolayer of coverage. The main difference between the desorption of the two adsorbates was the temperature of the terminal (lowest coverage) desorption energy site. The highest terminal desorption energy for cesium occurred on the W(110) surface at a temperature of 1200 K, while barium does not start to desorb from the W(110) surface until the temperature reaches approximately 1700 K. The temperature difference between the binding states of cesium and barium on all three of the substrates allowed for the adsorption and desorption of cesium without altering the barium adlayer. The desorption behavior of cesium from the various barium/substrate surfaces, like the work function change, was also very similar. As the coverage of pre -adsorbed barium increased, the activation energy of the cesium

  11. Modified method of surface plasmons in metal superlattices

    NASA Astrophysics Data System (ADS)

    Zhang, Yu-Liang; Wang, Xuan-Zhang

    2015-05-01

    We present a modified method to solve the surface plasmons (SPs) of semi-infinite metal/dielectric superlattices and predicted new SP modes in physics. We find that four dispersion-equation sets and all possible SP modes are determined by them. Our analysis and numerical calculations indicate that besides the SP mode obtained in the original theory, the other two SP modes are predicted, which have either a positive group velocity or a negative group velocity. We also point out the possible defect in the previous theoretical method in accordance to the linear algebra principle. Project supported by the National Natural Science Foundation of China (Grant No. 11074061).

  12. Surface functionalization of metal organic frameworks for mixed matrix membranes

    DOEpatents

    Albenze, Erik; Lartey, Michael; Li, Tao; Luebke, David R.; Nulwala, Hunaid B.; Rosi, Nathaniel L.; Venna, Surendar R.

    2017-03-21

    Mixed Matrix Membrane (MMM) are composite membranes for gas separation and comprising a quantity of inorganic filler particles, in particular metal organic framework (MOF), dispersed throughout a polymer matrix comprising one or more polymers. This disclosure is directed to MOF functionalized through addition of a pendant functional group to the MOF, in order to improve interaction with a surrounding polymer matrix in a MMM. The improved interaction aids in avoiding defects in the MMM due to incompatible interfaces between the polymer matrix and the MOF particle, in turn increasing the mechanical and gas separation properties of the MMM. The disclosure is also directed to a MMM incorporating the surface functionalized MOF.

  13. Super-Absorbent polymer gels for oil and grease removal from metal and non-metal surfaces

    USDA-ARS?s Scientific Manuscript database

    The objective of this research is to develop a new surface cleaning technology for removal of oil, grease and particulate matters from metal and non-metal surfaces. It is desired that the cleaner is in solid form and is VOC-exempt, HAP-free, non-toxic, non-corrosive, non-ozone depleting, recyclable...

  14. Surface structure determinations of crystalline ionic thin films grown on transition metal single crystal surfaces by low energy electron diffraction

    SciTech Connect

    Roberts, Joel Glenn

    2000-05-01

    The surface structures of NaCl(100), LiF(100) and alpha-MgCl2(0001) adsorbed on various metal single crystals have been determined by low energy electron diffraction (LEED). Thin films of these salts were grown on metal substrates by exposing the heated metal surface to a molecular flux of salt emitted from a Knudsen cell. This method of investigating thin films of insulators (ionic salts) on a conducting substrate (metal) circumvents surface charging problems that plagued bulk studies, thereby allowing the use of electron-based techniques to characterize the surface.

  15. Theory of catalytic dissociation of hydrogen atoms on a metal surface

    SciTech Connect

    Konstantinov, O. V. Dymnikov, V. D.; Mittsev, M. A.

    2008-08-15

    The model of hydrogen atom ionization near a metal surface is discussed on the basis of a comparison between the metal work function and the atom ionization energy. In the theoretical calculation, it is shown that the hydrogen atom ionization energy decreases when the atom approaches the metal surface. The ionization energy vanishes when the distance between proton and the metal surface is somewhat less than the Bohr radius.

  16. Immobilization of polymer microgels containing metal nanocatalysts onto inorganic surfaces

    NASA Astrophysics Data System (ADS)

    Papoutsakis, L.; Frysali, M. A.; Kaliva, M.; Vamvakaki, M.; Anastasiadis, S. H.

    2013-03-01

    This study is concerned with the attachment of electrostatically and sterically stabilized polymer microgel particles containing either amino (poly(2-(diethylamino)ethyl methacrylate), PDEA) or carboxylic acid (poly(acrylic acid), PAA; poly(methacrylic acid), PMMA) functional groups onto inorganic surfaces. The microgels are prepared by emulsion radical polymerization and are utilized as nanoreactors for the synthesis of metal nanoparticles to be used as nanocatalysts; Pd and Ru nanoparticles have been synthesized. The attachment of the microgel particles onto the various surfaces, which can potentially be used as the walls of microfluidic reactors, is studied; glass, silicon and alumina were used as substrates. We investigated the effects of parameters such as concentration of the suspension, substrate orientation whereas we utilized various recipes for ``trapping'' the microgel particles within interfaces to achieve their deposition onto the inorganic surfaces. The durability of the microgel particles attached onto the surfaces against hydration and shear forces was tested utilizing repeated immersion of the surfaces into water undergoing mechanically-generated hydrodynamic flow. Part of this research was sponsored by the European Union (POLYCAT; grant agreement CP-IP 246095-2)

  17. Model for outgassing of water from metal surfaces

    SciTech Connect

    Li, Minxu; Dylla, Fred

    1993-06-01

    Numerous measurements of outgassing from metal surfaces show that the outgassing obeys a power law of the form Q=Q{sub 10}t{sup -alpha}, where alpha is typically near unity. For unbaked systems, outgassing is dominated by water. This work demonstrates that alpha is a function of the water vapor exposure during venting of the system, and the physical properties of the passivation oxide layer on the surface. An analytic expression for the outgassing rate is derived based on the assumption that the rate of water diffusing through the passivation oxide layer to the surface governs the rate of its release into the vacuum. The source distribution function for the desorbing water is assumed to be a combination of a Gaussian distribution centered at the interior surface driven by atmospheric exposure, and a uniform concentration throughout the bulk. We have measured the outgassing rate from a clean stainless-steel (type 304) chamber as a function of water exposure to the chamber surface from <1 to 600 monolayers. The measured outgassing rate data show that alpha tends to 0.5 for low H{sub 2}O exposures and tends to 1.5 for high H{sub 2}O exposures as predicted by the model.

  18. A comparison of several surface finish measurement methods as applied to ground ceramic and metal surfaces

    SciTech Connect

    Blau, P.J.; Martin, R.L.; Riester, L.

    1996-01-01

    Surface finish is one of the most common measures of surface quality of ground ceramics and metal parts and a wide variety of methods and parameters have been developed to measure it. The purpose of this investigation was to compare the surface roughness parameters obtained on the same two specimens from three different types of measuring instruments: a traditional mechanical stylus system, a non-contact laser scanning system, and the atomic force microscope (two different AFM systems were compared). The same surface-ground silicon nitride and Inconel 625 alloy specimens were used for all measurements in this investigation. Significant differences in arithmetic average roughness, root-mean-square roughness, and peak-to-valley roughness were obtained when comparing data from the various topography measuring instruments. Non-contact methods agreed better with the others on the metal specimen than on the ceramic specimen. Reasons for these differences include the effective dimensions and geometry of the probe with respect to the surface topography; the reflectivity of the surface, and the type of filtering scheme Results of this investigation emphasize the importance of rigorously specifying the manner of surface roughness measurement when either reporting roughness data or when requesting that roughness data be provided.

  19. Effects of Surface Roughness on Stagnation Heat Transfer of Impinging Liquid Jet on Metal Surface

    NASA Astrophysics Data System (ADS)

    Lee, Jungho

    The liquid jet impingement with phase change heat transfer has long been an attractive method of cooling especially in steelmaking process and heat treatment in metals. The current study focuses on making detailed measurements of the stagnation-point heat transfer as a jet impinges on the rough metal surfaces at high temperature nominally up to 900°C. The local heat flux measurements are introduced by a novel experimental technique in which test block assemblies with cartridge heaters and thermocouples are used to measure the heat flux distribution on the surface of hot steel plate as a function of heat flux gauge. The effects of surface roughness on the stagnation-point heat transfer were investigated for well-characterized four rough surfaces with root-mean-square average roughness heights ranging from 40 to 80 µm. The results show that surface protrusions on rough surface can penetrate the thermal sublayer in the stagnation point and thus increase the heat transfer. The heat transfer enhancement mechanism on roughened surface can be investigated by the different boiling regimes.

  20. Adsorption of spent fuel storage pool contaminants into metal surfaces

    SciTech Connect

    Reaves, K.; Kunze, J.; Lu, Kang ); Bennett, P.C. )

    1990-01-01

    Shipping casks, after being submerged in spent fuel pools for the purpose of loading or unloading fuel, resist complete removal of the adsorbed contamination. To systematically study the mechanisms involved, 122 metal surface samples were immersed in the spent fuel storage pool of the Callaway Power Plant for periods of 7 to 30 days. After being removed from the pool, all samples were washed and wiped (with cloth) using demineralized water. They were then gamma counted for absolute activity, by using Eu-152 as an energy efficiency calibrator, applied uniformly to unexposed sample surfaces. Swipes were taken after each of 3 days of such environmental conditioning. Following this conditioning, selected samples were again counted to determine absolute contamination remaining on the samples. 2 refs., 1 tab.

  1. Temporal extent of surface potentials between closely spaced metals.

    PubMed

    Pollack, S E; Schlamminger, S; Gundlach, J H

    2008-08-15

    Variations in the electrostatic surface potential between the proof mass and electrode housing in the space-based gravitational wave mission Laser Interferometer Space Antenna (LISA) is one of the largest contributors of noise at frequencies below a few mHz. Torsion balances provide an ideal test bed for investigating these effects in conditions emulative of LISA. Our apparatus consists of a Au coated Cu plate brought near a Au coated Si plate pendulum suspended from a thin W wire. We have measured a white noise level of 30 microV/sqrt Hz above approximately 0.1 mHz, rising at lower frequencies, for the surface potential variations between these two closely spaced metals.

  2. Thermodynamic aspects of dehydrogenation reactions on noble metal surfaces

    SciTech Connect

    Svane, K. L. Hammer, B.

    2014-11-07

    The reaction free energy for dehydrogenation of phenol, aniline, thiophenol, benzoic acid, and 1,4-benzenediol on the close packed copper, silver, and gold surfaces has been studied by density functional theory calculations. Dehydrogenation of thiophenol is found to be favourable on all three surfaces while aniline does not dehydrogenate on any of them. For phenol, benzenediol and benzoic acid dehydrogenation is favourable on copper and silver only, following the general trend of an increasing reaction free energy when going form gold to silver to copper. This trend can be correlated with the changes in bond lengths within the molecule upon dehydrogenation. While copper is able to replace hydrogen, leaving small changes in the bond lengths of the aromatic ring, the metal-molecule bond is weaker for silver and gold, resulting in a partial loss of aromaticity. This difference in bond strength leads to pronounced differences in adsorption geometries upon multiple dehydrogenations.

  3. The Impedance Due to the Roughness of Metallic Surface

    SciTech Connect

    Bane, Karl L.F.; Chao, Alex W.; Ng, Cho-K.; /SLAC

    2011-08-26

    In some future accelerator designs, such as that of the Linear Coherent Light Source (LCLS), the bunch is very short, with an rms length on the order of 10's of microns, and the effective skin depth of the vacuum chamber walls can be very small compared to 1 micron. If the skin depth is small compared to the scale of the surface roughness then the wakefield due to the walls will be dominated by the roughness, and not by the wall resistance. To estimate the wakefields of a rough, metallic surface we begin with a simple, analytical model. Then we apply the MAFIA 3-dimensional, time-domain computer module, T3 to check and find the correct coefficient for the model.

  4. The Impedance Due to the Roughness of Metallic Surface.

    NASA Astrophysics Data System (ADS)

    Bane, Karl L. F.; Chao, Alex W.; Ng, Cho-K.

    1997-05-01

    In some future accelerator designs, such as that of the Linear Coherent Light Source (LCLS), the bunch is very short, with an rms length on the order of 10's of microns, and the effective skin depth of the vacuum chamber walls can be very small compared to 1 micron. If the skin depth is small compared to the scale of the surface roughness then the wakefield due to the walls will be dominated by the roughness, and not by the wall resistance. To estimate the wakefields of a rough, metallic surface we begin with a simple, analytical model. Then we apply the MAFIA 3-dimensional, time-domain computer module, T3 to check and find the correct coefficient for the model.

  5. Surface plasmon polaritons on metal cylinders with dielectric core

    NASA Astrophysics Data System (ADS)

    Schröter, Ursula; Dereux, Alain

    2001-09-01

    Metal-cladded dielectric cylinders with submicron diameters may serve to model coated tips used in near-field scanning optical microscopy. The signal measured may be greatly influenced by resonance effects due to eigenmodes of the probe. Especially, using a photon scanning tunneling microscope setup, gold-coated tips have been found to detect a signal proportional to the magnetic field distributions [E. Devaux et al., Phys. Rev. B 62, 10 504 (2000)]. This effect is attributed to cylindrical surface plasmons. We present here fully retarded calculations of the dispersion and field patterns of the nonradiative plasmon modes in cylindrical geometry. We study the effect of varying the cylinder radius on the surface plasmon dispersion, thus justifying that the cylinder is a useful model for near-field probes in spite of their slightly conical shape.

  6. Visualization of terahertz surface waves propagation on metal foils

    PubMed Central

    Wang, Xinke; Wang, Sen; Sun, Wenfeng; Feng, Shengfei; Han, Peng; Yan, Haitao; Ye, Jiasheng; Zhang, Yan

    2016-01-01

    Exploitation of surface plasmonic devices (SPDs) in the terahertz (THz) band is always beneficial for broadening the application potential of THz technologies. To clarify features of SPDs, a practical characterization means is essential for accurately observing the complex field distribution of a THz surface wave (TSW). Here, a THz digital holographic imaging system is employed to coherently exhibit temporal variations and spectral properties of TSWs activated by a rectangular or semicircular slit structure on metal foils. Advantages of the imaging system are comprehensively elucidated, including the exclusive measurement of TSWs and fall-off of the time consumption. Numerical simulations of experimental procedures further verify the imaging measurement accuracy. It can be anticipated that this imaging system will provide a versatile tool for analyzing the performance and principle of SPDs. PMID:26729652

  7. Liquid Metal Pump Technologies for Nuclear Surface Power

    NASA Technical Reports Server (NTRS)

    Polzin, Kurt A.

    2007-01-01

    Multiple liquid metal pump options are reviewed for the purpose of determining the technologies that are best suited for inclusion in a nuclear reactor thermal simulator intended to rest prototypical space nuclear surface power system components. Conduction, induction and thermoelectric electromagnetic pumps are evaluated based on their performance characteristics and the technical issues associated with incorporation into a reactor system. A thermoelectric electromagnetic pump is selected as the best option for use in NASA-MSFC's Fission Surface Power-Primary Test Circuit reactor simulator based on its relative simplicity, low power supply mass penalty, flight heritage, and the promise of increased pump efficiency over those earlier pump designs through the use of skutterudite thermoelectric elements.

  8. Surface binding of toxins and heavy metals by probiotics.

    PubMed

    Zoghi, Alaleh; Khosravi-Darani, Kianoush; Sohrabvandi, Sara

    2014-01-01

    Removal of toxic metals and toxins using microbial biomass has been introduced as an inexpensive, new promising method on top of conventional methods for decontamination of food, raw material and concentrated. In this article the potential application of lactic acid bacteria and yeasts as the most familiar probiotics to eliminate, inactivate or reduce bioavailability of contamination in foods and feed has been reviewed. After fast glance to beneficial health effects and preservative properties of lactic acid bacteria, the mechanisms which explain antibacterial and antifungal efficiency as well as their antifungal metabolites are mentioned. Then the article has been focused on potential application of single strain or combination of lactic acid bacteria for removal of heavy metals (copper, lead, cadmium, chromium, arsenic), cyanotoxins (microcystin-LR, -RR, -LF) and mycotoxins (aflatoxin B1, B2, B2a, M1, M2, G1, G2, patulin, ochratoxin A, deoxynivalenol, fumonisin B1 and B2, 3-acetyldeoxynivalenol, deoxynivalenol, fusarenon, nivalenol, diacetoxyscirpenol, HT-2 and T-2 toxin, zearalenone and its derivative, etc) from aqueous solutions in vitro. Wherever possible the mechanism of decontamination and the factors influencing yield of removal are discussed. Some factors which can facilitate metal removal capacity of lactic acid bacteria including the strains, surface charge, pH, temperature, presence of other cations are introduced. The cell wall structure of lactic acid bacteria and yeasts are also introduced for further explanation of mechanism of action in complex binding of probiotic to contaminants and strength of mycotoxin- bacterium interaction.

  9. Dielectric tuned surface plasmon resonances on metallic gratings

    NASA Astrophysics Data System (ADS)

    Hauser, Adam; Flaherty, Bill; Law, Ka Ming; Mikheev, Evgeny; Kajdos, Adam; Stemmer, Susanne; Allen, S. James

    2015-03-01

    We explore the effect of substrate dielectric constant on the dispersion of infrared surface plasmons supported by micron scale metal gratings. Of particular interest are substrate dielectrics that can be tuned by electric fields and thereby make possible gated plasmonic devices. Angle resolved s and p polarized reflectivity is used to observe the plasmon dispersion for Pt gratings on various oxide dielectrics and heterostructures, LSAT, SrTiO3, Nb:SrTiO3 and LSAT/SrTiO3/GdTiO3. Most striking is the shift in the plasmon dispersion upon Nb doping of SrTiO3 caused by the free carrier contribution to the dielectric constant. We focus our attention on a metal-oxide-metal heterostructure, Pt/BaxSr1-xTiO3/Pt-grating that serves to confine the infrared field to the electric field modulated region enhancing the potential for a gated plasmonic structure. Supported by the ONR MURI ``Extreme electron density electronics'' N00014-12-0976.

  10. Microstructure and Surface Damage in Retrieved Metal-on-Metal Hip Arthroplasties.

    PubMed

    Fernández-Fairen, Mariano; Punset, Miquel; Murcia-Asensio, Antonio; Ferrero-Manzanal, Francisco; Sueiro, José; Gil, Javier

    2017-07-08

    Besides promising results of metal-on-metal (MOM) hip arthroplasty (HA), frequent failures have been reported even in the short term. Many host, surgical, design, metallurgical, and processing factors have been evoked in the base of these events. We have tried to characterize and to evaluate metallurgical and processing features present in this type of implants. The acetabular and femoral components of 20 MOM HAs collected from a multicenter retrieval program were examined. All the specimens were inspected with naked eye, with confocal microscopy and vertical scanning interferometry, scanning electron microscopy, back-scattered electron imaging, and energy-dispersive X-ray spectroscopy, in 25 zones of each articular component. Gas pores, shrinkage voids and holes of detached carbides, carbides on surface, embedded particles, scratches and marks of wear, surface discoloration, surface deposits, and tribochemical reaction layers were widely dispersed through a substantial percentage of the total bearing surface in all the implanted components. Surface cup and head voids, and cup scratches showed significant correlation with the clearance of pair. A higher surface damage of the cup and head was observed mainly in the low clearance prostheses. There was no other significant correlation or difference in the incidence and importance of any of these defects between resurfacing hip arthroplasties and total hip arthroplasties, or according to the pair diameter. Some metallurgical features and surface damage were significantly present in the retrieved implants of MoM HAs. It would be desirable to improve the structure and metallurgical characteristics of these implants to avoid those effects and optimize their performance. Copyright © 2017 Elsevier Inc. All rights reserved.

  11. Electron Scattering at Surfaces and Interfaces of Transition Metals

    NASA Astrophysics Data System (ADS)

    Zheng, Pengyuan

    The effect of surfaces on the electron transport at reduced scales is attracting continuous interest due to its broad impact on both the understanding of materials properties and their application for nanoelectronics. The size dependence of for conductor's electrical resistivity rho due to electron surface scattering is most commonly described within the framework of Fuchs and Sondheimer (FS) and their various extensions, which uses a phenomenological scattering parameter p to define the probability of electrons being elastically (i.e. specularly) scattered by the surface without causing an increase of rho at reduced size. However, a basic understanding of what surface chemistry and structure parameters determine the specularity p is still lacking. In addition, the assumption of a spherical Fermi surface in the FS model is too simple for transition metals to give accurate account of the actual surface scattering effect. The goal of this study is to develop an understanding of the physics governing electron surface/interface scattering in transition metals and to study the significance of their Fermi surface shape on surface scattering. The advancement of the scientific knowledge in electron surface and interface scattering of transition metals can provide insights into how to design high-conductivity nanowires that will facilitate the viable development of advanced integrated circuits, thermoelectric power generation and spintronics. Sequential in situ and ex situ transport measurements as a function of surface chemistry demonstrate that electron surface/interface scattering can be engineered by surface doping, causing a decrease in the rho. For instance, the rho of 9.3-nm-thick epitaxial and polycrystalline Cu is reduced by 11--13% when coated with 0.75 nm Ni. This is due to electron surface scattering which exhibits a specularity p = 0.7 for the Cu-vacuum interface that transitions to completely diffuse (p = 0) when exposed to air. In contrast, Ni-coated surfaces

  12. Observation of radiative surface plasmons in metal-oxide-metal tunnel junctions

    NASA Technical Reports Server (NTRS)

    Donohue, J. F.; Yang, E. Y.

    1986-01-01

    A peak in the UV region of the spectrum of light emitted from metal-oxide-metal (MOM) tunnel junctions has been observed at room temperature. Both the amplitude and wavelength of the peak are sensitive to applied junction bias. The UV peak corresponds to the normal or radiative surface plasmon mode while a visible peak, also present in the present spectra and reported in past MOM literature, is due to the tangential or nonradiative mode. The radiative mode requires no surface roughness or gratings for photon coupling. The results show that it is possible to obtain radiative surface plasmon production followed by a direct decay into photons with MOM tunnel diodes. A MOM diode with a double anode structure is found to emit light associated only with the nonradiative mode. The thickness dependence of the UV peak, along with the experimental results of the double anode MOM diode and the ratio of the UV peak to visible peak, support the contention that the UV light emission is indeed due to the radiative surface plasmon.

  13. Isocyanide ligands adsorbed on metal surfaces: applications in catalysis, nanochemistry, and molecular electronics.

    PubMed

    Angelici, Robert J; Lazar, Mihaela

    2008-10-20

    Knowledge of the coordination chemistry and reactivity of isocyanide ligands in transition-metal complexes forms the basis for understanding the adsorption and reactions of isocyanides on metal surfaces. In this overview, we explore reactions (often catalytic) of isocyanides adsorbed on metal surfaces that reflect their patterns of reactivity in metal complexes. We also examine applications of isocyanide adsorption to the stabilization of metal nanoparticles, the functionalization of metal electrodes, and the creation of conducting organic-metal junctions in molecule-scale electronic devices.

  14. Reactions of metal ions at surfaces of hydrous iron oxide

    USGS Publications Warehouse

    Hem, J.D.

    1977-01-01

    Cu, Ag and Cr concentrations in natural water may be lowered by mild chemical reduction involving ferric hydroxide-ferrous ion redox processes. V and Mo solubilities may be controlled by precipitation of ferrous vanadate or molybdate. Concentrations as low as 10-8.00 or 10-9.00 M are readily attainable for all these metals in oxygen-depleted systems that are relatively rich in Fe. Deposition of manganese oxides such as Mn3O4 can be catalyzed in oxygenated water by coupling to ferrous-ferric redox reactions. Once formed, these oxides may disproportionate, giving Mn4+ oxides. This reaction produces strongly oxidizing conditions at manganese oxide surfaces. The solubility of As is significantly influenced by ferric iron only at low pH. Spinel structures such as chromite or ferrites of Cu, Ni, and Zn, are very stable and if locally developed on ferric hydroxide surfaces could bring about solubilities much below 10-9.00 M for divalent metals near neutral pH. Solubilities calculated from thermodynamic data are shown graphically and compared with observed concentrations in some natural systems. ?? 1977.

  15. Colloidal Quantum Dot Red-Shifting on Textured Metal Surfaces

    NASA Astrophysics Data System (ADS)

    Ferri, Christopher; Grimes, Anthony; Ghosh, Sayantani

    2011-03-01

    We have studied the influence of textured metal surfaces on the emission of an ensemble of colloidal CdSe/ZnS core-shell quantum dots (QDs). The texture was generated by sputter coating a thin film of Gold Paladium (AuPd) on a thermoplastic Polydimethylsiloxane (PDMS) sheet. We used two separate protocols to generate two types of surfaces. We constrained some substrates such that they shrunk along only one planar dimension (uniaxial) while some were allowed to shrink along both planar directions (biaxial). The uniaxial substrates forced the metal to buckle along one dimension and the biaxial substrates buckled into a pseudorandom texture. We found that the QDs deposited on the biaxial substrates had a general red shift in the emission wavelength compared to their emission in solution, which also corresponded to a change in the temporal dynamics of the emission. The QDs on the uniaxial substrates showed a change in their temporal dynamics corresponding to plasmonic coupling, but no spectral shift. We hypothesize that the effects observed on the biaxial substrates are caused by the Franz-Keldysh effect. National Science Foundation.

  16. Giant and switchable surface activity of liquid metal via surface oxidation

    PubMed Central

    Khan, Mohammad Rashed; Eaker, Collin B.; Bowden, Edmond F.; Dickey, Michael D.

    2014-01-01

    We present a method to control the interfacial tension of a liquid alloy of gallium via electrochemical deposition (or removal) of the oxide layer on its surface. In sharp contrast with conventional surfactants, this method provides unprecedented lowering of surface tension (∼500 mJ/m2 to near zero) using very low voltage, and the change is completely reversible. This dramatic change in the interfacial tension enables a variety of electrohydrodynamic phenomena. The ability to manipulate the interfacial properties of the metal promises rich opportunities in shape-reconfigurable metallic components in electronic, electromagnetic, and microfluidic devices without the use of toxic mercury. This work suggests that the wetting properties of surface oxides—which are ubiquitous on most metals and semiconductors—are intrinsic “surfactants.” The inherent asymmetric nature of the surface coupled with the ability to actively manipulate its energetics is expected to have important applications in electrohydrodynamics, composites, and melt processing of oxide-forming materials. PMID:25228767

  17. On the HSAB based estimate of charge transfer between adsorbates and metal surfaces

    NASA Astrophysics Data System (ADS)

    Kokalj, Anton

    2012-01-01

    The applicability of the HSAB based electron charge transfer parameter, Δ N, is analyzed for molecular and atomic adsorbates on metal surfaces by means of explicit DFT calculations. For molecular adsorbates Δ N gives reasonable trends of charge transfer if work function is used for electronegativity of metal surface. For this reason, calculated work functions of low Miller index surfaces for 11 different metals are reported. As for reactive atomic adsorbates, e.g., N, O, and Cl, the charge transfer is proportional to the adatom valence times the electronegativity difference between the metal surface and the adatom, where the electronegativity of metal is represented by a linear combination of atomic Mulliken electronegativity and the work function of metal surface. It is further shown that the adatom-metal bond strength is linearly proportional to the metal-to-adatom charge transfer thus making the Δ N parameter a useful indicator to anticipate the corresponding adsorption energy trends.

  18. Surface treatments of metal supports for photocatalysis applications

    NASA Astrophysics Data System (ADS)

    Montecchio, Francesco; Chinungi, Don; Lanza, Roberto; Engvall, Klas

    2017-04-01

    One of the most important challenges, for scaling up a photocatalytic system for VOCs abatement to full-scale, is the design of a suitable photocatalyst support. The support has to firmly immobilize the photocatalyst, without using an organic adhesive, and should also withstand relatively high mechanical stresses. Metals may be effectively implemented as a support material, after a corrugation of the surface with electrochemical treatments. In the present work, we treated stainless steel and aluminum supports, evaluating the surface modifications due to the electrochemical treatments, with scanning electron microscopy (SEM) and confocal microscopy. Five samples showing the highest degree of restructuring were selected and spray coated with P25, a TiO2 photocatalyst, evaluating the mechanical stability of the coating with a standard tape test method. One particular stainless steel sample presented a superior surface restructuring and coating stability. The photocatalytic activity of this sample, evaluated measuring the complete oxidation of acetaldehyde, was tested for 15 h, and compared with sample of TiO2-P25 on a ceramic support. The stainless steel exhibited a constant performance after an initial stabilization period. The stainless steel sample showed a slightly higher activity, due to the surface restructuring, increasing the irradiated area available for the coated photocatalyst.

  19. Metal nanocrystal/metal-organic framework core/shell nanostructure from selective self-assembly induced by localization of metal ion precursors on nanocrystal surface.

    PubMed

    Ohhashi, Takashi; Tsuruoka, Takaaki; Matsuyama, Tetsuhiro; Takashima, Yohei; Nawafune, Hidemi; Minami, Hideto; Akamatsu, Kensuke

    2015-08-01

    Metal nanocrystal/metal-organic framework core/shell nanostructures have been constructed using metal ion-trapped nanocrystals as scaffolds through a selective self-assembly of framework components on the nanocrystal surfaces. The resulting nanostructures exhibit unique catalytic activity toward nitrophenol analogs.

  20. 40 CFR 52.253 - Metal surface coating thinner and reducer.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 3 2013-07-01 2013-07-01 false Metal surface coating thinner and... PROGRAMS (CONTINUED) APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS California § 52.253 Metal surface... Counties Air Basin portion). (iii) This section is rescinded for metal parts and products coaters which...

  1. 40 CFR 52.253 - Metal surface coating thinner and reducer.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 3 2014-07-01 2014-07-01 false Metal surface coating thinner and... PROGRAMS (CONTINUED) APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS California § 52.253 Metal surface... Counties Air Basin portion). (iii) This section is rescinded for metal parts and products coaters which...

  2. 40 CFR 52.253 - Metal surface coating thinner and reducer.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 3 2010-07-01 2010-07-01 false Metal surface coating thinner and... PROGRAMS (CONTINUED) APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS California § 52.253 Metal surface... Counties Air Basin portion). (iii) This section is rescinded for metal parts and products coaters which...

  3. 40 CFR 52.253 - Metal surface coating thinner and reducer.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 3 2012-07-01 2012-07-01 false Metal surface coating thinner and... PROGRAMS (CONTINUED) APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS California § 52.253 Metal surface... Counties Air Basin portion). (iii) This section is rescinded for metal parts and products coaters which...

  4. 40 CFR 52.253 - Metal surface coating thinner and reducer.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 3 2011-07-01 2011-07-01 false Metal surface coating thinner and... PROGRAMS (CONTINUED) APPROVAL AND PROMULGATION OF IMPLEMENTATION PLANS California § 52.253 Metal surface... Counties Air Basin portion). (iii) This section is rescinded for metal parts and products coaters which...

  5. 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.

  6. Raising the shields: PCR in the presence of metallic surfaces protected by tailor-made coatings.

    PubMed

    Scherag, Frank D; Brandstetter, Thomas; Rühe, Jürgen

    2014-10-01

    The implementation of PCR reactions in the presence of metallic surfaces is interesting for the generation of novel bioanalytical devices, because metals exhibit high mechanical stability, good thermal conductivity, and flexibility during deformation. However, metallic substrates are usually non-compatible with enzymatic reactions such as PCR due to poisoning of the active center of the enzyme or nonspecific adsorption of the enzymeto the metal surface, which could result in protein denaturation. We present a method for the generation of polymer coatings on metallic surfaces which are designed to minimize protein adsorption and also prevent the release of metal ions. These coatings consist of three layers covalently linked to each other; a self-assembled monolayer to promote adhesion, a photochemically generated barrier layer and a photochemically generated hydrogel. The coatings can be deposited onto aluminum, stainless steel, gold and copper surfaces. We compare PCR efficiencies in the presence of bare metallic surfaces with those of surfaces treated with the novel coating system.

  7. A Method to Manipulate Surface Tension of a Liquid Metal via Surface Oxidation and Reduction.

    PubMed

    Eaker, Collin B; Khan, M Rashed; Dickey, Michael D

    2016-01-26

    Controlling interfacial tension is an effective method for manipulating the shape, position, and flow of fluids at sub-millimeter length scales, where interfacial tension is a dominant force. A variety of methods exist for controlling the interfacial tension of aqueous and organic liquids on this scale; however, these techniques have limited utility for liquid metals due to their large interfacial tension. Liquid metals can form soft, stretchable, and shape-reconfigurable components in electronic and electromagnetic devices. Although it is possible to manipulate these fluids via mechanical methods (e.g., pumping), electrical methods are easier to miniaturize, control, and implement. However, most electrical techniques have their own constraints: electrowetting-on-dielectric requires large (kV) potentials for modest actuation, electrocapillarity can affect relatively small changes in the interfacial tension, and continuous electrowetting is limited to plugs of the liquid metal in capillaries. Here, we present a method for actuating gallium and gallium-based liquid metal alloys via an electrochemical surface reaction. Controlling the electrochemical potential on the surface of the liquid metal in electrolyte rapidly and reversibly changes the interfacial tension by over two orders of magnitude ( ̴500 mN/m to near zero). Furthermore, this method requires only a very modest potential (< 1 V) applied relative to a counter electrode. The resulting change in tension is due primarily to the electrochemical deposition of a surface oxide layer, which acts as a surfactant; removal of the oxide increases the interfacial tension, and vice versa. This technique can be applied in a wide variety of electrolytes and is independent of the substrate on which it rests.

  8. Evaluation of ultrasonic cavitation of metallic and non-metallic surfaces

    NASA Technical Reports Server (NTRS)

    Mehta, Narinder K.

    1992-01-01

    1,1,2 trichloro-1,2,2 trifluoro ethane (CFC-113) commercially known as Freon-113 is the primary test solvent used for validating the cleaned hardware at the Kennedy Space Center (KSC). Due to the ozone depletion problem, the current United States policy calls for the phase out of Freons by 1995. NASAs chlorofluorocarbon (CFC) replacement group at KSC has opted to use water as a replacement fluid for the validation process since water is non-toxic, inexpensive, and is environmentally friendly. The replacement validation method calls for the ultrasonification of the small parts with water at 52 C for a cycle or two of 10 min duration wash using commercial ultrasonic baths. In this project, experimental data was obtained to assess the applicability of the proposed validation method for any damage of the metallic and non-metallic surfaces resulting from ultrasonic cavitation.

  9. Frequency selective heterojunction metal-insulator-metal mirror for surface plasmons

    NASA Astrophysics Data System (ADS)

    Hwang, Yongsop; Shin, Jonghwa; Kim, Jae-Eun; Park, Hae Yong; Kee, Chul-Sik

    2011-06-01

    The authors introduce a mode-gap mirror for surface plasmon polaritons in a metal-insulator-metal (MIM) structure. At the heterojunction of MIMs which consists of two MIMs of different insulators, it is shown that a mode gap exists for a certain frequency range and the junction works as an effective mirror. Transmission and reflection properties of plasmonic modes at the interface of the heterojunction are investigated, and explained by the band theory. By showing that the mirror has high reflection and transmission of nearly zero, it is verified that the frequency range in which no plasmonic modes exist is an actual mode-gap range. It is also shown that by varying both the thickness and the dielectric constant of the insulator layer, one can select the frequency range in which the reflection coefficient is greater than 0.9.

  10. Decay and propagation properties of symmetric surface plasmon polariton mode in metal-insulator-metal waveguide

    NASA Astrophysics Data System (ADS)

    Yang, Hongyan; Li, Jianqing; Xiao, Gongli

    2017-07-01

    Decay and propagation properties of symmetric surface plasmon polariton (SPP) mode based on metal-insulator-metal (MIM) waveguide are investigated numerically. SPP mode is excited through a dipole embedded in Al2 O3 layer of Au /Al2 O3 / Au structure. We demonstrate that the distance between the dipole and Al2 O3 / Au interface is an important tunable parameter to influence the decay properties. The electric/magnetic field intensity horizontal and vertical decay lengths of symmetric SPP mode are 19 nm and 24 nm, respectively. Moreover, the propagation length along Al2 O3 / Au interface of symmetric SPP mode depends on Al2 O3 layer thickness. The maximal propagation length reaches 0.608 μm with Al2 O3 layer thickness of 100 nm. These values can provide a theoretical reference for designing a high-performance SPP source using Au /Al2 O3 / Au structure.

  11. Surface field analysis of splitting of orbitals of atoms and ions approaching a metal surface.

    NASA Technical Reports Server (NTRS)

    Rao, P. V. S.; Waber, J. T.

    1971-01-01

    The splitting of p- and d-orbitals of an atom or an ion which is caused by the locally varying potential near the surface of a realistic metal has been studied for bcc and fcc substrates. A quasi-ionic model is reasonable at close distance, inasmuch as the electron gas does not completely screen the ionic cores. The arrangement of ion cores near the surface causes the potential to vary in three dimensions. Expressions for energy levels were derived for an unsymmetric group using the quasi-ionic model and techniques used in the treatment of crystal field of nearest neighbors. A number of cases involving ions, as well as atoms in the vicinity of a metal substrate were numerically evaluated.

  12. Electronic and structural properties of transition metals and transition metal surfaces

    SciTech Connect

    Chan, C.T.

    1985-01-01

    Electronic and structural properties of transition metals and transition metal surfaces are studied theoretically from first principles, with emphasis on understanding their properties under different physical and chemical environments. A new general self-consistency procedures for calculating the electronic structure of crystalline solids is developed and applied to extend a first-principles pseudopotential linear combination of atomic orbitals (LCOA) method to full point-by-point self-consistency. This scheme is tested by applying to a study of the structural and electronic properties of Si and W - prototypical systems of very different bonding characters. The importance of self-consistency is investigated. Structural properties of Mo and W in the bcc, fcc, and hcp structures are calculated with the new scheme. Equilibrium lattice constants, cohesive energies, bulk moduli, differences in structural energies, and Milliken population analyses are obtained. Structural properties of the W(001)(1 x 1) surface are also calculated with the same method. Surface energy, top layer relaxation, and relaxation energy are obtained with good agreement with available experimental data. The electronic structures of PdH and Pd/sub 4/H are calculated by a pseudopotential mixed basis approach with emphasis on the nature of the Pd-H bonding state and the effect of changing hydrogen concentration.

  13. Spatial Variability and Distribution of the Metals in Surface Runoff in a Nonferrous Metal Mine

    PubMed Central

    Ren, Bozhi; Chen, Yangbo; Zhu, Guocheng; Wang, Zhenghua; Zheng, Xie

    2016-01-01

    The spatial variation and distribution features of the metals tested in the surface runoff in Xikuangshan Bao Daxing miming area were analyzed by combining statistical methods with a geographic information system (GIS). The results showed that the maximum concentrations of those five kinds of the metals (Sb, Zn, Cu, Pb, and Cd) in the surface runoff of the antimony mining area were lower than the standard value except the concentration of metal Ni. Their concentrations were 497.1, 2.0, 1.8, 22.2, and 22.1 times larger than the standard value, respectively. This metal pollution was mainly concentrated in local areas, which were seriously polluted. The variation coefficient of Sb, Zn, Cu, Ni, Pb, and Cd was between 0.4 to 0.6, wherein the Sb's spatial variability coefficient is 50.56%, indicating a strong variability. Variation coefficients of the rest of metals were less than 50%, suggesting a moderate variability. The spatial structure analysis showed that the squared correlation coefficient (R2) of the models fitting for Sb, Zn, Cu, Ni, Pb, and Cd was between 0.721 and 0.976; the ratio of the nugget value (C0) to the abutment value (C + C0) was between 0.0767 and 0.559; the semivariogram of Sb, Zn, Ni, and Pb was in agreement with a spherical model, while semivariogram of Cu and Cd was in agreement with Gaussian model, and both had a strong spatial correlation. The trend and spatial distribution indicated that those pollution distributions resulting from Ni, Pb, and Cd are similar, mainly concentrated in both ends of north and south in eastern part. The main reasons for the pollution were attributed to the residents living, transportation, and industrial activities; the Sb distribution was concentrated mainly in the central part, of which the pollution was assigned to the mining and the industrial activity; the pollution distributions of Zn and Cu were similar, mainly concentrated in both ends of north and south as well as in west; the sources of the metals were

  14. Lifting the mirror symmetry of metal surfaces: decoupling the electronic and physical manifestations of surface chirality.

    PubMed

    Mulligan, Andrew; Lane, Ian; Rousseau, Gilles B D; Johnston, Shona M; Lennon, David; Kadodwala, Malcolm

    2006-01-19

    Naturally occurring metal surfaces possess planes of mirror symmetry on the nanometer-length scale. This mirror symmetry can be lifted and chirality "physically" conveyed onto a surface by adsorbing a chiral molecule. Until now, it has not been known whether the conveying of chirality is limited to just the physical structure or whether it goes deeper and permeates the electronic structure of the underlying surface. By using optically active second harmonic generation (OA-SHG), it is demonstrated that the adsorption of some, but not all, chiral molecules can reversibly, and without significant structural rearrangement, measurably lift the mirror symmetry of the surface electronic structure of a metal. It is proposed that the ability of a chiral molecule to place a significant "chiral perturbation" on the electronic structure of a surface is correlated to its adsorption geometry. The microscopic origins of the observed optical activity are also discussed in terms of classical models of chirality. The results of the study challenge current models of how chiral adsorbates induce enantioselectivity in the chemical/physical behavior of heterogeneous systems, which are based on geometric/stereochemical arguments, by suggesting that chiral electronic perturbations could play a role.

  15. Influence of etching and annealing on evolution of surface structure of metallic glass

    NASA Astrophysics Data System (ADS)

    Ushakov, Ivan V.; Feodorov, Victor A.; Permyakova, Inga J.

    2004-04-01

    Evolution of surface structure of metallic glass subjected to etching was investigated. The changes of surface structure of metallic glass 82K3XCP after chemical etching and different modes of annealing were studied. Samples of metallic glass were etched in solutions of sulphurous acid with different concentration. Corrosion-resistance was determined. The dependence of corrosion rate on acid concentration was found. Characteristic concentric circumferences on the etching surface were investigated. Their formation mechanism is discussed. Crystallization on surface stimulated by both acid and annealing was examined. The formation of first dendrites on surface of annealed metallic glass and their evolution were investigated.

  16. Modeling and verifying the polarizing reflectance of real-world metallic surfaces.

    PubMed

    Berger, Kai; Weidlich, Andrea; Wilkie, Alexander; Magnor, Marcus

    2012-01-01

    Using measurements of real-world samples of metals, the proposed approach verifies predictions of bidirectional reflectance distribution function (BRDF) models. It employs ellipsometry to verify both the actual polarizing effect and the overall reflectance behavior of the metallic surfaces.

  17. Metal thin film growth on multimetallic surfaces: From quaternary metallic glass to binary crystal

    SciTech Connect

    Jing, Dapeng

    2010-01-01

    The work presented in this thesis mainly focuses on the nucleation and growth of metal thin films on multimetallic surfaces. First, we have investigated the Ag film growth on a bulk metallic glass surface. Next, we have examined the coarsening and decay of bilayer Ag islands on NiAl(110) surface. Third, we have investigated the Ag film growth on NiAl(110) surface using low-energy electron diffraction (LEED). At last, we have reported our investigation on the epitaxial growth of Ni on NiAl(110) surface. Some general conclusions can be drawn as follows. First, Ag, a bulk-crystalline material, initially forms a disordered wetting layer up to 4-5 monolayers on Zr-Ni-Cu-Al metallic glass. Above this coverage, crystalline 3D clusters grow, in parallel with the flatter regions. The cluster density increases with decreasing temperature, indicating that the conditions of island nucleation are far-from-equilibrium. Within a simple model where clusters nucleate whenever two mobile Ag adatoms meet, the temperature-dependence of cluster density yields a (reasonable) upper limit for the value of the Ag diffusion barrier on top of the Ag wetting layer of 0.32 eV. Overall, this prototypical study suggests that it is possible to grow films of a bulk-crystalline metal that adopt the amorphous character of a glassy metal substrate, if film thickness is sufficiently low. Next, the first study of coarsening and decay of bilayer islands has been presented. The system was Ag on NiAl(110) in the temperature range from 185 K to 250 K. The coarsening behavior, has some similarities to that seen in the Ag(110) homoepitaxial system studied by Morgenstern and co-workers. At 185 K and 205 K, coarsening of Ag islands follows a Smoluchowski ripening pathway. At 205 K and 250 K, the terrace diffusion limited Ostwald ripening dominants. The experimental observed temperature for the transition from SR to OR is 205 K. The SR exhibits anisotropic island diffusion and the OR exhibits 1D decay of island

  18. Magnetism and surface structure of atomically controlled ultrathin metal films.

    SciTech Connect

    Shiratsuchi, Yu.; Yamamoto, M.; Bader, S. D.; Materials Science Division; Osaka Univ.

    2007-01-01

    We review the correlation of magnetism and surface structure in ultrathin metal films, including the tailoring of novel magnetic properties using atomic scale control of the nanostructure. We provide an overview of modern fabrication and characterization techniques used to create and explore these fascinating materials, and highlight important phenomena of interest. We also discuss techniques that control and characterize both the magnetic and structural properties on an atomic scale. Recent advances in the development and applications of these techniques allow nanomagnetism to be investigated in an unprecedented manner. A system cannot necessarily retain a two-dimensional structure as it enters the ultrathin region, but it can transform into a three-dimensional, discontinuous structure due to the Volmer-Weber growth mechanism. This structural transformation can give rise to superparamagnetism. During this evolution, competing factors such as interparticle interactions and the effective magnetic anisotropy govern the magnetic state. These magnetic parameters are influenced by the nanostructure of the film. In particular, controlling the magnetic anisotropy is critical for determining the magnetic properties. Surface effects play especially important roles in influencing both the magnitude and direction of the magnetic anisotropy in ultrathin films. By properly altering the surface structure, the strength and direction of the magnetic anisotropy are controlled via spin-orbit and/or dipole interactions.

  19. Electron Scattering at Surfaces of Epitaxial Metal Layers

    NASA Astrophysics Data System (ADS)

    Chawla, Jasmeet Singh

    In the field of electron transport in metal films and wires, the 'size effect' refers to the increase in the resistivity of the films and wires as their critical dimensions (thickness of film, width and height of wires) approach or become less than the electron mean free path lambda, which is, for example, 39 nm for bulk copper at room temperature. This size-effect is currently of great concern to the semiconductor industry because the continued downscaling of feature sizes has already lead to Cu interconnect wires in this size effect regime, with a reported 2.5 times higher resistivity for 40 nm wide Cu wires than for bulk Cu. Silver is a possible alternate material for interconnect wires and titanium nitride is proposed as a gate metal in novel field-effect-transistors. Therefore, it is important to develop an understanding of how the growth, the surface morphology, and the microstructure of ultrathin (few nanometers) Cu, Ag and TiN layers affect their electrical properties. This dissertation aims to advance the scientific knowledge of electron scattering at surfaces (external surfaces and grain boundaries), that are, the primary reasons for the size-effect in metal conductors. The effect of surface and grain boundary scattering on the resistivity of Cu thin films and nanowires is separately quantified using (i) in situ transport measurements on single-crystal, atomically smooth Cu(001) layers, (ii) textured polycrystalline Cu(111) layers and patterned wires with independently varying grain size, thickness and line width, and (iii) in situ grown interfaces including Cu-Ta, Cu-MgO, Cu-vacuum and Cu-oxygen. In addition, the electron surface scattering is also measured in situ for single-crystal Ag(001), (111) twinned epitaxial Ag(001), and single-crystal TiN(001) layers. Cu(001), Ag(001), and TiN(001) layers with a minimum continuous thickness of 4, 3.5 and 1.8 nm, respectively, are grown by ultra-high vacuum magnetron sputter deposition on MgO(001) substrates with

  20. Rate of Heat Transfer from Finned Metal Surfaces

    NASA Technical Reports Server (NTRS)

    Taylor, G Fayette; Rehbock, A

    1930-01-01

    The object was to evaluate the factors which control the rate of heat transfer to a moving current of air from finned metal surfaces similar to those used on aircraft engine cylinders. The object was to establish data which will enable the finning of cooling surfaces to be designed to suit the particular needs of any specific application. Most of the work was done on flat copper specimens 6 inches square, upon which were mounted copper fins with spacings varying from 1/2 inch to 1/12 inch. All fins were 1 inch deep, 6 inches long, and .020 inch thick. The results of the investigation are given in the form of curves included here. In general, it was found that for specimens of this kind, the effectiveness of a given fin does not decrease very rapidly until its distance from adjacent fins has been reduced to 1/9 or 1/10 of an inch. A formula for the heat transfer from a flat surface without fins was developed, and an approximate formula for the finned specimens is suggested.

  1. Enhanced Electron-Phonon Coupling at Metal Surfaces

    SciTech Connect

    Plummer, Ward E.

    2010-08-04

    The Born-Oppenheimer approximation (BOA) decouples electronic from nuclear motion, providing a focal point for most quantum mechanics textbooks. However, a multitude of important chemical, physical and biological phenomena are driven by violations of this approximation. Vibronic interactions are a necessary ingredient in any process that makes or breaks a covalent bond, for example, conventional catalysis or enzymatically delivered biological reactions. Metastable phenomena associated with defects and dopants in semiconductors, oxides, and glasses entail violation of the BOA. Charge exchange in inorganic polymers, organic slats and biological systems involves charge- induced distortions of the local structure. A classic example is conventional superconductivity, which is driven by the electron-lattice interaction. High-resolution angle-resolved photoemission experiments are yielding new insight into the microscopic origin of electron-phonon coupling (EPC) in anisotropic two-dimensional systems. Our recent surface phonon measurement on the surface of a high-Tc material clearly indicates an important momentum dependent EPC in these materials. In the last few years we have shifted our research focus from solely looking at electron phonon coupling to examining the structure/functionality relationship at the surface of complex transition metal compounds. The investigation on electron phonon coupling has allowed us to move to systems where there is coupling between the lattice, the electrons and the spin.

  2. Radiation damage from single heavy ion impacts on metal surfaces

    SciTech Connect

    Donnelly, S.E.; Birtcher, R.C.

    1998-06-01

    The effects of single ion impacts on the surfaces of films of Au, Ag, In and Pb have been studied using in-situ transmission electron microscopy. On all of these materials, individual ion impacts produce surface craters, in some cases, with associated expelled material. The cratering efficiency scales with the density of the irradiated metal. For very thin Au foils ({approx} 20--50 nm), in some cases individual ions are seen to punch small holes completely through the foil. Continued irradiation results in a thickening of the foil. The process giving rise to crater and hole formation and other changes observed in the thin foils has been found to be due to pulsed localized flow--i.e. melting and flow due to the thermal spikes arising from individual ion impacts. Experiments carried out on thin films of silver sandwiched between SiO{sub 2} layers have indicated that pulsed localized flow also occurs in this system and contributes to the formation of Ag nanoclusters in SiO{sub 2}--a system of interest for its non-linear optical properties. Calculation indicates that, when ion-induced, collision cascades occur near surfaces (within {approx} 5 nm) with energy densities sufficient to cause melting, craters are formed. Crater formation occurs as a result of the explosive outflow of material from the hot molten core of the cascade. Processes occurring in the sandwiched layer are less well understood.

  3. Ferroplasmons: Intense Localized Surface Plasmons in Metal-Ferromagnetic Nanoparticles

    SciTech Connect

    Sachan, Ritesh; Malasi, Abhinav; Ge, Jingxuan; Yadavali, Sagar P; Gangopadhyay, Anup; Krishna, Dr. Hare; Garcia, Hernando; Duscher, Gerd J M; Kalyanaraman, Ramki

    2014-01-01

    Interaction of photons with matter at length scales far below their wavelengths has given rise to many novel phenomena, including localized surface plasmon resonance (LSPR). However, LSPR with narrow bandwidth (BW) is observed only in a select few noble metals, and ferromagnets are not among them. Here, we report the discovery of LSPR in ferromagnetic Co and CoFe alloy (8% Fe) in contact with Ag in the form of bimetallic nanoparticles prepared by pulsed laser dewetting. These plasmons in metal-erromagnetic nanostructures, or ferroplasmons (FP) for short, are in the visible spectrum with comparable intensity and BW to those of the LSPRs from the Ag regions. This finding was enabled by electron energy-loss mapping across individual nanoparticles in a monochromated scanning transmission electron microscope. The appearance of the FP is likely due to plasmonic interaction between the contacting Ag and Co nanoparticles. Since there is no previous evidence for materials that simultaneously show ferromagnetism and such intense LSPRs, this discovery may lead to the design of improved plasmonic materials and applications. It also demonstrates that materials with interesting plasmonic properties can be synthesized using bimetallic nanostructures in contact with each other.

  4. Organometallic Chemistry and catalysis on gold metal surfaces

    SciTech Connect

    Angelici, Robert J.

    2007-11-21

    As in transition metal complexes, C{triple_bond}N-R ligands adsorbed on powdered gold undergo attack by amines to give putative diaminocarbene groups on the gold surface. This reaction forms the basis for the discovery of a gold metal-catalyzed reaction of C{triple_bond}N-R, primary amines (R{prime}NH{sub 2}) and O{sub 2} to give carbodiimides (R{prime}-N{double_bond}C{double_bond}N-R). An analogous reaction of C{triple_bond}O, RNH{sub 2}, and O{sub 2} gives isocyanates (R-N{double_bond}C{double_bond}O), which react with additional amine to give urea (RNH){sub 2}C{double_bond}O products. The gold-catalyzed reaction of C{triple_bond}N-R with secondary amines (HNR{prime}{sub 2}) and O{sub 2} gives mixed ureas RNH(CO)NR{prime}{sub 2}. In another type of gold-catalyzed reaction, secondary amines HN(CH{sub 2}R){sub 2} react with O{sub 2} to undergo dehydrogenation to the imine product, RCH{double_bond}N(CH{sub 2}R). Of special interest is the high catalytic activity of gold powder, which is otherwise well-known for its poor catalytic properties.

  5. Wear resistance of a metal surface modified with minerals

    NASA Astrophysics Data System (ADS)

    Kislov, S. V.; Kislov, V. G.; Balasch, P. V.; Skazochkin, A. V.; Bondarenko, G. G.; Tikhonov, A. N.

    2016-02-01

    The article describes the advantages of the new technology of mineral coating of metal products for the friction pair of mechanical systems. It presents the research results of the wear rate of the samples made of 12X13 steel (X12Cr13) with mineral layers, in the experiments with a piston ring sliding inside a cylinder liner with grease. The wear rate of the samples with mineral layers is lower almost by two factors than that of the samples made of grey foundry iron and untreated samples. As the result of slip/rolling abrasion tests of parts with mineral layers under conditions of high contact pressure, a suggestion was made concerning probable mechanics of surface wear.

  6. Surface-mediated light transmission in metal nanoparticle chains

    NASA Astrophysics Data System (ADS)

    Compaijen, P. Jasper; Malyshev, Victor A.; Knoester, Jasper

    2013-05-01

    We study theoretically the efficiency of the transmission of optical signals through a linear chain consisting of identical and equidistantly spaced silver metal nanoparticles. Two situations are compared: the transmission efficiency through an isolated chain and through a chain in close proximity of a reflecting substrate. The Ohmic and radiative losses in each nanoparticle strongly affect the transmission efficiency of an isolated chain and suppress it to large extent. It is shown that the presence of a reflecting interface may enhance the guiding properties of the array. The reason for this is the energy exchange between the surface plasmon polaritons (SPPs) of the array and the substrate. We focus on the dependence of the transmission efficiency on the frequency and polarization of the incoming light, as well as on the influence of the array-interface spacing. Sometimes the effect of these parameters turns out to be counterintuitive, reflecting a complicated interplay of several transmission channels.

  7. Automatic surface inspection of metal tubes by artificial vision

    SciTech Connect

    Truchetet, F.; Jender, H.; Gorria, P.; Paindavoine, M.; Ngo, P.A.

    1997-04-01

    The authors present in this article the different problems they have been facing with the design of an artificial vision inspection system for metallic tubes. They focus on the adopted solutions, the implementation of these solutions, and an estimation of the system performance in an industrial environment. The solution is based on the use of a set of linear CCD cameras. The displacement of the object under inspection ensures the achievement of a two dimensional image. The choice of two different points of view enables us to consider tint and embossing variations. The introduction of an angular correction reduces the scattering of the response due to the nonplanarity of the surface under control. The calculation of the parameters in a low level language enables us to perform a real time inspection (running speed: 1m/s [3.3 ft/s]).

  8. Foam and gel methods for the decontamination of metallic surfaces

    DOEpatents

    Nunez, Luis; Kaminski, Michael Donald

    2007-01-23

    Decontamination of nuclear facilities is necessary to reduce the radiation field during normal operations and decommissioning of complex equipment. In this invention, we discuss gel and foam based diphosphonic acid (HEDPA) chemical solutions that are unique in that these solutions can be applied at room temperature; provide protection to the base metal for continued applications of the equipment; and reduce the final waste form production to one step. The HEDPA gels and foams are formulated with benign chemicals, including various solvents, such as ionic liquids and reducing and complexing agents such as hydroxamic acids, and formaldehyde sulfoxylate. Gel and foam based HEDPA processes allow for decontamination of difficult to reach surfaces that are unmanageable with traditional aqueous process methods. Also, the gel and foam components are optimized to maximize the dissolution rate and assist in the chemical transformation of the gel and foam to a stable waste form.

  9. Surface-Emitting Distributed Feedback Terahertz Quantum-Cascade Lasers in Metal-Metal Waveguides

    NASA Technical Reports Server (NTRS)

    Kumar, Sushil; Williams, Benjamin S.; Qin, Qi; Lee, Alan W. M.; Hu, Qing; Reno, John L.

    2007-01-01

    Single-mode surface-emitting distributed feedback terahertz quantumcascade lasers operating around 2.9 THz are developed in metal-metal waveguides. A combination of techniques including precise control of phase of reflection at the facets, and u e of metal on the sidewalls to eliminate higher-order lateral modes allow robust single-mode operation over a range of approximately 0.35 THz. Single-lobed far-field radiation pattern is obtained using a pi phase-shift in center of the second-order Bragg grating. A grating device operating at 2.93 THz lased up to 149 K in pulsed mode and a temperature tuning of 19 .7 GHz was observed from 5 K to 147 K. The same device lased up to 78 K in continuous-wave (cw) mode emitting more than 6 m W of cw power at 5 K. ln general, maximum temperature of pulsed operation for grating devices was within a few Kelvin of that of multi-mode Fabry-Perot ridge lasers

  10. Surface-Emitting Distributed Feedback Terahertz Quantum-Cascade Lasers in Metal-Metal Waveguides

    NASA Technical Reports Server (NTRS)

    Kumar, Sushil; Williams, Benjamin S.; Qin, Qi; Lee, Alan W. M.; Hu, Qing; Reno, John L.

    2007-01-01

    Single-mode surface-emitting distributed feedback terahertz quantumcascade lasers operating around 2.9 THz are developed in metal-metal waveguides. A combination of techniques including precise control of phase of reflection at the facets, and u e of metal on the sidewalls to eliminate higher-order lateral modes allow robust single-mode operation over a range of approximately 0.35 THz. Single-lobed far-field radiation pattern is obtained using a pi phase-shift in center of the second-order Bragg grating. A grating device operating at 2.93 THz lased up to 149 K in pulsed mode and a temperature tuning of 19 .7 GHz was observed from 5 K to 147 K. The same device lased up to 78 K in continuous-wave (cw) mode emitting more than 6 m W of cw power at 5 K. ln general, maximum temperature of pulsed operation for grating devices was within a few Kelvin of that of multi-mode Fabry-Perot ridge lasers

  11. 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

  12. The electrochemisty of surface modified <10 nm metal oxide nanoparticles

    NASA Astrophysics Data System (ADS)

    Roberts, Joseph J. P.

    Chapter One provides a general introduction of the research on metal oxide nanoparticles (MOx), highlighting their synthesis, surface modification, and functionalization. Emphasis is given to the different synthetic route for producing small (<10 nm) MOx nanoparticles with narrow size distributions. Different methods for modifying their surface with small organic molecules are discussed with focus given to silanes and phosphates. Furthermore, functionalizing surface modified nanoparticles for specific functions is addressed, with markers for analytically relevant nanoscale quantification being the primary focus. Chapter Two describes in detail the thermal degradation synthesis used for the generation of small MOx nanoparticles. It demonstrates the versatile of the synthesis by successfully synthesizing ZrO 2 and IrO2 nanoparticles. Preliminary work involving the formation of Bi2S3, Bi2O3, and RuO2 nanomaterials is also addressed. The solvothermal synthesis of indium tin oxide (ITO) is also shown for comparison to ITO produced by thermal degradation. Chapter Three details the surface modification of ITO nanoparticles and subsequent electrochemical tagging with a ferrocene moiety. ITO nanoparticles were synthesized via thermal degradation. These nanoparticles underwent a ligand exchange with a covalently binding mondentate silane terminated with a primary amine. Acyl chloride coupling between the amine and chlorocarbonylferrocene provided an electrochemical tag to quantify the level of surface modification. Electrochemisty of the quasi-diffusing nanoparticles was evaluated via cyclic voltammetry (CV), chronoamperometry (CA), and mircodisk electrode (microE) experiments. Chapter Four investigates spectroscopic tagging of ITO and ZrO2 nanoparticles as well as electrochemical tagging of ZrO 2 and IrO2 nanoparticles. An unbound azo-dye was synthesized and attempts were made to attach the dye to the surface of ITO nanoparticles. Imine couple between a spectroscopic tag

  13. First-principles study of semiconductor and metal surfaces

    NASA Astrophysics Data System (ADS)

    Kim, Sungho

    In this dissertation, we study the electronic and geometric structure of semiconductors and metal surfaces based on quantum mechanical first-principles calculations. We determine the geometry of vacancy defects of hydrogen adsorbed on a Pd(111) surface by treating the motion of a hydrogen atom, in addition to electrons, quantum mechanically. The calculated ground state wave function has high probability density in the hcp site located at the center of the vacancy instead of the fcc sites where the potential is minimum and hydrogen atoms on a Pd(111) surface normally adsorb. The geometry of quantum mechanically determined divacancy provides a simple and clear explanation for the scanning tunneling microscopy (STM) images of these defects that appear as three-lobed objects as observed in recent experiments [Mitsui, et al, Nature 422, 705 (2003)]. We employ the same principle to successfully elucidate the STM images of larger size vacancy defects. Our model also provides a compelling argument to explain the unusual recent experimental result that aggregates of three or more hydrogen vacancies are much more active in adsorption of hydrogen molecules while two-vacancy defects are never inactive. The InAs (110) surfaces appear lower than GaSb in STM images. This height difference is caused primarily by differences in the electronic structure of the two materials according to our calculations in a good agreement with measurements. In contrast, local variations in the apparent height of (110) surface atoms at InSb- or GaAs-like interfaces arise primarily from geometric distortions associated with local differences in bond length. The arsenic atoms adsorb preferably at the bridge sites between the dimerized Sb atoms on Sb-terminating (001) surfaces. Indium atoms, on the other hand, have somewhat equal probabilities at a few different sites on Ga-terminating (001) surfaces. Our calculated energies for atomic intermixing indicate that anion exchanges are exothermic for As

  14. A review of the application of anodization for the fabrication of nanotubes on metal implant surfaces.

    PubMed

    Minagar, Sepideh; Berndt, Christopher C; Wang, James; Ivanova, Elena; Wen, Cuie

    2012-08-01

    Metal implants are the best choice for the long-term replacement of hard tissue, such as hip and knee joints, because of their excellent mechanical properties. Titanium and its alloys, due to their self-organized oxide layer, which protects the surface from corrosion and prevents ion release, are widely accepted as biocompatible metal implants. Surface modification is essential for the promotion of the osseointegration of these biomaterials. Nanotubes fabricated on the surface of metal implants by anodization are receiving ever-increasing attention for surface modification. This paper provides an overview of the employment of anodization for nanotubes fabricated on the surface of titanium, titanium alloys and titanium alloying metals such as niobium, tantalum and zirconium metal implants. This work explains anodic oxidation and the manner by which nanotubes form on the surface of the metals. It then assesses this topical research to indicate how changes in anodizing conditions influence nanotube characteristics such as tube diameters and nanotube-layer thickness.

  15. Coverage and chemical dependence of adsorbate-induced bond weakening in metal substrate surfaces

    SciTech Connect

    Sette, F.; Hashizume, T.; Comin, F.; MacDowell, A.A.; Citrin, P.H.

    1988-09-19

    Strongly coverage-dependent outward relaxation and enhanced in-plane vibrational amplitudes of metal surface atoms have been observed from S- and Cl-covered Ni(001) and Cu(001) by means of temperature- and polarization-dependent surface extended-x-ray-absorption fine-structure measurements. These results explicitly demonstrate the weakening of both interlayer and intralayer metal-metal substrate bonds. A model based on adsorbate-metal charge rearrangement explains these chemisorption-induced changes in the geometric and dynamic properties of the metal surface.

  16. High surface area, electrically conductive nanocarbon-supported metal oxide

    DOEpatents

    Worsley, Marcus A.; Han, Thomas Yong-Jin; Kuntz, Joshua D.; Cervantes, Octavio; Gash, Alexander E.; Baumann, Theodore F.; Satcher, Jr., Joe H.

    2015-07-14

    A metal oxide-carbon composite includes a carbon aerogel with an oxide overcoat. The metal oxide-carbon composite is made by providing a carbon aerogel, immersing the carbon aerogel in a metal oxide sol under a vacuum, raising the carbon aerogel with the metal oxide sol to atmospheric pressure, curing the carbon aerogel with the metal oxide sol at room temperature, and drying the carbon aerogel with the metal oxide sol to produce the metal oxide-carbon composite. The step of providing a carbon aerogel can provide an activated carbon aerogel or provide a carbon aerogel with carbon nanotubes that make the carbon aerogel mechanically robust.

  17. High surface area, electrically conductive nanocarbon-supported metal oxide

    SciTech Connect

    Worsley, Marcus A; Han, Thomas Yong-Jin; Kuntz, Joshua D; Cervanted, Octavio; Gash, Alexander E; Baumann, Theodore F; Satcher, Jr., Joe H

    2014-03-04

    A metal oxide-carbon composite includes a carbon aerogel with an oxide overcoat. The metal oxide-carbon composite is made by providing a carbon aerogel, immersing the carbon aerogel in a metal oxide sol under a vacuum, raising the carbon aerogel with the metal oxide sol to atmospheric pressure, curing the carbon aerogel with the metal oxide sol at room temperature, and drying the carbon aerogel with the metal oxide sol to produce the metal oxide-carbon composite. The step of providing a carbon aerogel can provide an activated carbon aerogel or provide a carbon aerogel with carbon nanotubes that make the carbon aerogel mechanically robust.

  18. Microexplosions initiated by a microwave capillary torch on a metal surface at atmospheric pressure

    SciTech Connect

    Gritsinin, S. I.; Davydov, A. M.; Kossyi, I. A.

    2015-07-15

    The interaction of the plasma of a microwave capillary argon torch with a metal surface was studied experimentally. It is shown that the interaction of the plasma jet generated by the capillary plasma torch with the metal in atmospheric-pressure air leads to the initiation of microexplosions (sparks) on the metal surface. As a result, the initially smooth surface acquires a relief in the form of microtips and microcraters. The possibility of practical application of the observed phenomenon is discussed.

  19. Spoof surface plasmon modes on doubly corrugated metal surfaces at terahertz frequencies

    NASA Astrophysics Data System (ADS)

    Liu, Yong-Qiang; Kong, Ling-Bao; Du, Chao-Hai; Liu, Pu-Kun

    2016-06-01

    Spoof surface plasmons (SSPs) have many potential applications such as imaging and sensing, communications, innovative leaky wave antenna and many other passive devices in the microwave and terahertz (THz) spectrum. The extraordinary properties of SSPs (e.g. extremely strong near field, enhanced beam-wave interaction) make them especially attractive for developing novel THz electronic sources. SSP modes on doubly corrugated metal surfaces are investigated and analyzed both theoretically and numerically in this paper. The analytical SSP dispersion expressions of symmetric and anti-symmetric modes are obtained with a simplified modal field expansion method; the results are also verified by the finite integration method. Additionally, the propagation losses are also considered for real copper surfaces with a limited constant conductivity in a THz regime. It is shown that the asymptotical frequency of the symmetric mode at the Brillouin boundary decreases along with the decreased gap size between these two corrugated metal surfaces while the asymptotical frequency increases for the anti-symmetric mode. The anti-symmetric mode demonstrates larger propagation losses than the symmetric mode. Further, the losses for both symmetric and anti-symmetric modes decrease when this gap size enlarges. By decreasing groove depth, the asymptotical frequency increases for both the symmetric and the anti-symmetric mode, but the variation of propagation losses is more complicated. Propagation losses increase along with the increased period. Our studies on the dispersion characteristics and propagation losses of SSP modes on this doubly corrugated metallic structure with various parameters is instructive for numerous applications such as waveguides, circuitry systems with high integration, filters and powerful electronic sources in the THz regime.

  20. 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.

  1. Review of the highlights of X-ray studies of liquid metal surfaces

    SciTech Connect

    Pershan, P. S.

    2014-12-14

    X-ray studies of the interface between liquid metals and their coexisting vapor are reviewed. After a brief discussion of the few elemental liquid metals for which the surface Debye-Waller effect is sufficiently weak to allow measurement, this paper will go on to discuss the various types of surface phenomena that have been observed for liquid metal alloys. These include surface adsorption, surface freezing, surface aggregation of nm size atomic clusters, and surface chemistry that leads to new 3D crystalline phases.

  2. Apparatus for coating a surface with a metal utilizing a plasma source

    DOEpatents

    Brown, Ian G.; MacGill, Robert A.; Galvin, James E.

    1991-01-01

    An apparatus and method for coating or layering a surface with a metal utilizing a metal vapor vacuum arc plasma source. The apparatus includes a trigger mechanism for actuating the metal vacuum vapor arc plasma source in a pulsed mode at a predetermined rate. The surface or substrate to be coated or layered is supported in position with the plasma source in a vacuum chamber. The surface is electrically biased for a selected period of time during the pulsed mode of operation of the plasma source. Both the pulsing of the metal vapor vacuum arc plasma source and the electrical biasing of the surface are synchronized for selected periods of time.

  3. Simple theory of elastically deformed metals: Surface energy, stress, and work function

    NASA Astrophysics Data System (ADS)

    Kiejna, Adam; Pogosov, Valentin V.

    2000-10-01

    The effect of uniaxial strain on surface properties of simple metals is considered within the stabilized jellium model. The modified equations for the stabilization energy of the deformed Wigner-Seitz cells are derived as a function of the bulk electron density and the given deformation. The model requires as input the density parameter rs, the Poisson ratio, and Young's modulus of the metal. The results for surface energy, surface stress, and work function of simple metals calculated within the self-consistent Kohn-Sham method are also presented and discussed. A consistent explanation of the independent experiments on stress-induced contact potential difference at metal surfaces is given.

  4. Surface-hydrogen-induced metallization and rumpling in thin BaTi O3 films

    NASA Astrophysics Data System (ADS)

    Fredrickson, K. D.; Demkov, A. A.

    2016-12-01

    We study theoretically metallization and polarization enhancement effects of H adsorption at the Ti O2 -terminated (001) BaTi O3 (BTO) surface. The clean BTO slab does not polarize because the slab is too thin to support a ferroelectric state. We find that the metallization of the surface is a strong function of hydrogen coverage and that the insulating surfaces do not support a rumpling or polarization in BTO films, whereas all metallic surfaces do so. The donated charge from the adsorbed H transforms the Ti O2 into a metallic capping layer, stabilizing the ferroelectric state.

  5. Surface-controlled dislocation multiplication in metal micropillars

    PubMed Central

    Weinberger, Christopher R.; Cai, Wei

    2008-01-01

    Understanding the plasticity and strength of crystalline materials in terms of the dynamics of microscopic defects has been a goal of materials research in the last 70 years. The size-dependent yield stress observed in recent experiments of submicrometer metallic pillars provides a unique opportunity to test our theoretical models, allowing the predictions from defect dynamics simulations to be directly compared with mechanical strength measurements. Although depletion of dislocations from submicrometer face-centered-cubic (FCC) pillars provides a plausible explanation of the observed size-effect, we predict multiplication of dislocations in body-centered-cubic (BCC) pillars through a series of molecular dynamics and dislocation dynamics simulations. Under the combined effects from the image stress and dislocation core structure, a dislocation nucleated from the surface of a BCC pillar generates one or more dislocations moving in the opposite direction before it exits from the surface. The process is repeatable so that a single nucleation event is able to produce a much larger amount of plastic deformation than that in FCC pillars. This self-multiplication mechanism suggests a need for a different explanation of the size dependence of yield stress in FCC and BCC pillars. PMID:18787126

  6. Surface coating for prevention of metallic seed migration in tissues.

    PubMed

    Lee, Hyunseok; Lee, Won Seok; Park, Jong In; Son, Kwang-Jae; Park, Min; Bang, Young-bong; Choy, Young Bin; Ye, Sung-Joon

    2015-06-01

    In radiotherapy, metallic implants often detach from their deposited sites and migrate to other locations. This undesirable migration could cause inadequate dose coverage for permanent brachytherapy and difficulties in image-guided radiation delivery for patients. To prevent migration of implanted seeds, the authors propose a potential strategy to use a biocompatible and tissue-adhesive material called polydopamine. In this study, nonradioactive dummy seeds that have the same geometry and composition as commercial I-125 seeds were coated in polydopamine. Using scanning electron microscopy and x-ray photoelectron spectroscopy, the surface of the polydopamine-coated and noncoated seeds was characterized. The detachment stress between the two types of seeds and the tissue was measured. The efficacy of polydopamine-coated seed was investigated through in vitro migration tests by tracing the seed location after tissue implantation and shaking for given times. The cytotoxicity of the polydopamine coating was also evaluated. The results of the coating characterization have shown that polydopamine was successfully coated on the surface of the seeds. In the adhesion test, the polydopamine-coated seeds had 2.1-fold greater detachment stress than noncoated seeds. From the in vitro test, it was determined that the polydopamine-coated seed migrated shorter distances than the noncoated seed. This difference was increased with a greater length of time after implantation. The authors suggest that polydopamine coating is an effective technique to prevent migration of implanted seeds, especially for permanent prostate brachytherapy.

  7. Ionization of Rydberg atoms colliding with a metal surface

    SciTech Connect

    Sjakste, J.; Borisov, A. G.; Gauyacq, J. P.

    2006-04-15

    We report on a theoretical study of the ionization process of Xe* Rydberg atoms colliding with a metal surface, in the presence of an external electric field. The evolution of the Xe* outer electron is studied by a wave packet propagation approach, allowing to include all dynamical aspects of the collision, in particular nonadiabatic inter-Rydberg transitions. We investigate how the different Xe* Stark states formed in the external field couple together and ionize on the surface and how the different polarizations of the electronic cloud in the Xe* states are reflected in their ionization properties. We show that the presence of the external electric field can significantly perturb the dynamics of the ionization process. Our results account for recent results from Dunning et al. [Nucl. Inst. Meth. B 203, 69 (2003)]. In particular, it is explained how the external electric field present in the experimental procedure of Dunning et al. leads to the apparent absence of a polarization effect in the ionization process.

  8. Surface-controlled dislocation multiplication in metal micropillars.

    PubMed

    Weinberger, Christopher R; Cai, Wei

    2008-09-23

    Understanding the plasticity and strength of crystalline materials in terms of the dynamics of microscopic defects has been a goal of materials research in the last 70 years. The size-dependent yield stress observed in recent experiments of submicrometer metallic pillars provides a unique opportunity to test our theoretical models, allowing the predictions from defect dynamics simulations to be directly compared with mechanical strength measurements. Although depletion of dislocations from submicrometer face-centered-cubic (FCC) pillars provides a plausible explanation of the observed size-effect, we predict multiplication of dislocations in body-centered-cubic (BCC) pillars through a series of molecular dynamics and dislocation dynamics simulations. Under the combined effects from the image stress and dislocation core structure, a dislocation nucleated from the surface of a BCC pillar generates one or more dislocations moving in the opposite direction before it exits from the surface. The process is repeatable so that a single nucleation event is able to produce a much larger amount of plastic deformation than that in FCC pillars. This self-multiplication mechanism suggests a need for a different explanation of the size dependence of yield stress in FCC and BCC pillars.

  9. Surface coating for prevention of metallic seed migration in tissues

    SciTech Connect

    Lee, Hyunseok; Park, Jong In; Lee, Won Seok; Park, Min; Son, Kwang-Jae; Bang, Young-bong; Choy, Young Bin E-mail: sye@snu.ac.kr; Ye, Sung-Joon E-mail: sye@snu.ac.kr

    2015-06-15

    Purpose: In radiotherapy, metallic implants often detach from their deposited sites and migrate to other locations. This undesirable migration could cause inadequate dose coverage for permanent brachytherapy and difficulties in image-guided radiation delivery for patients. To prevent migration of implanted seeds, the authors propose a potential strategy to use a biocompatible and tissue-adhesive material called polydopamine. Methods: In this study, nonradioactive dummy seeds that have the same geometry and composition as commercial I-125 seeds were coated in polydopamine. Using scanning electron microscopy and x-ray photoelectron spectroscopy, the surface of the polydopamine-coated and noncoated seeds was characterized. The detachment stress between the two types of seeds and the tissue was measured. The efficacy of polydopamine-coated seed was investigated through in vitro migration tests by tracing the seed location after tissue implantation and shaking for given times. The cytotoxicity of the polydopamine coating was also evaluated. Results: The results of the coating characterization have shown that polydopamine was successfully coated on the surface of the seeds. In the adhesion test, the polydopamine-coated seeds had 2.1-fold greater detachment stress than noncoated seeds. From the in vitro test, it was determined that the polydopamine-coated seed migrated shorter distances than the noncoated seed. This difference was increased with a greater length of time after implantation. Conclusions: The authors suggest that polydopamine coating is an effective technique to prevent migration of implanted seeds, especially for permanent prostate brachytherapy.

  10. Proposed Heuristic Model for Fuzz Growth on Metal Surfaces

    NASA Astrophysics Data System (ADS)

    Ochoukov, Roman; Whyte, Dennis

    2011-10-01

    The growth of nano-scale rods, or fuzz, is observed experimentally on tungsten and molybdenum surfaces exposed to an incident He flux with ion energies >10 eV. It is experimentally determined that the growth of fuzz follows a diffusion-like equation as a function of the He exposure time t: x ~ (2Dt)1/2, where x is the fuzz thickness and D is the effective diffusion coefficient. This growth is consistent with the incident He flux Γo being reduced at a rate of d Γ(x)/dx = - αΓ (x)1/2 as the He ions traverse the fuzz. α is an integration constant. Based on the above assumption, we derived a relation between x, Γo, and t: x + 2 α-1 Γo-1/2 = (2Dt)1/2. The notable features of this equation, for a fixed exposure time, are: 1) the saturation of the fuzz thickness as Γo approaches ∞ and 2) the minimum threshold value of the incident He flux Γo required to initiate fuzz growth. Both of these features are experimentally observed. Another notable feature is that it requires a minimum He fluence Γotmin at the metal surface to initiate fuzz growth. Supported by USDoE award DE-FC02-99ER54512.

  11. Surface enrichment in hot-dipped metallic coatings investigated by Auger electron spectroscopy

    NASA Astrophysics Data System (ADS)

    Payling, R.; Mercer, P. D.

    1985-05-01

    The treatment, appearance, and corrosion resistance of metallic coatings are largely governed by the chemical composition of the surface. Auger electron spectroscopy shows that the surfaces of hot-dipped metallic coatings differ markedly from the bulk compositions of the coatings. For example, the surfaces of terne coatings, lead-tin alloys, contain little lead. The conventional galvanized coating, which is more than 99% zinc, has a predominantly aluminium oxide surface. Typical surface compositions of a range of hot-dipped metallic coatings are provided. A qualitative prediction of the dominant metallic species present on the surface of each of these coatings is presented in terms of the relative oxygen affinities of the metals. Theoretical equations for various mechanisms, such as atomic size mismatch, solubility, and oxidation, which could lead to surface segregation are considered, in order to place the experimental observations on a more quantitative basis.

  12. Urbanization increased metal levels in lake surface sediment and catchment topsoil of waterscape parks.

    PubMed

    Li, Hong-Bo; Yu, Shen; Li, Gui-Lin; Liu, Yi; Yu, Guang-Bin; Deng, Hong; Wu, Sheng-Chun; Wong, Ming-Hung

    2012-08-15

    Lake surface sediment is mainly derived from topsoil in its catchment. We hypothesized that distribution of anthropogenic metals would be homogenous in lake surface sediment and the lake's catchment topsoil. Anthropogenic metal distributions (cadmium (Cd), copper (Cu), lead (Pb), and zinc (Zn)) in fourteen waterscape parks were investigated in surface sediments and catchment topsoils and possible source homogeneity was tested using stable Pb isotopic ratio analysis. The parks were located along an urbanization gradient consisting of suburban (SU), developing urban (DIU), developed urban (DDU), and central urban core (CUC) areas in Shanghai, China. Results indicated that surface lake sediments and catchment topsoils in the CUC parks were highly contaminated by the investigated anthropogenic metals. Total metal contents in surface sediment and topsoil gradually increased along the urbanization gradient from the SU to CUC areas. Generally, the surface sediments had greater total metal contents than their catchment topsoils. These results suggest that urbanization drives the anthropogenic metal enrichment in both surface sediment and its catchment topsoil in the waterscape parks. Soil fine particles (<63 μm) and surface sediments had similar enrichment ratios of metals, suggesting that surface runoff might act as a carrier for metals transporting from catchment to lake. Stable Pb isotope ratio analysis revealed that the major anthropogenic Pb source in surface sediment was coal combustion as in the catchment topsoil. Urbanization also correlated with chemical fractionation of metals in both surface sediment and catchment topsoil. From the SU to the CUC parks, amounts of labile metal fractions increased while the residual fraction of those metals remained rather constant. In short, urbanization in Shanghai drives anthropogenic metal distribution in environmental matrices and the sources were homogenous. Copyright © 2012 Elsevier B.V. All rights reserved.

  13. The Growth of Metal Overlayers on Oxide Surfaces.

    NASA Astrophysics Data System (ADS)

    Mayer, Jeffrey Thomas

    1995-01-01

    The structural and chemical properties of metals on oxides have been analyzed by examining two very different adsorption systems. The first, Ni/SiO_2 , is representative of systems with a rather weak interaction between the metal overlayer and oxide substrate. The second system analyzed, Ti/TiO_2, is an example with very strong reactive adsorbate/substrate interaction. The surface and interface behavior of both systems are investigated using basic thermodynamic and kinetic concepts. The surface diffusion of nickel on a thermally -grown silicon dioxide thin film (5-50A), and the bulk diffusion of Ni through the SiO_2 film into the single crystal silicon substrate have been studied by x-ray photoelectron spectroscopy (XPS), high resolution electron energy loss spectroscopy (HREELS), low energy electron diffraction (LEED), and atomic force microscopy (AFM). Nickel agglomeration on the oxide occurs in the 100-850K regime, while bulk Ni diffusion through the thin oxide layer occurs in the 700-1050K regime. The onset of bulk Ni diffusion is dependent on oxide thickness; thicker oxides reduce the rate of Ni penetration. Above 950-1100K, the oxide desorbs leaving nickel disilicide on silicon. The study of nickel disilicide island formation on Si(111) (an outgrowth of the Ni/SiO_2 experiments) is reported. The kinetics of this system control a rather interesting series of metastable growth structures. Visually striking NiSi_2 crystallites are observed on the Si(111) surface by AFM. The nickel disilicide islands coalesce following a high temperature anneal (~1260K). The islands differ from those formed at lower temperature in both shape and orientation. These differences are explained by kinetically limited growth accompanying phase and surface segregation of Ni from the bulk silicon wafer, and condensation of a Ni-rich NiSi_{rm 2-x} liquid phase at the surface. Condensation from the liquid phase to NiSi_2 is concluded to be responsible for the structure of the crystallites

  14. The local metallicity-surface brightness relationship in galactic disks

    NASA Technical Reports Server (NTRS)

    Ryder, Stuart D.

    1995-01-01

    We present the results of a first attempt to employ multiaperture masks to obtain spectrophotometry of H II regions in nearby galaxies. A total of 97 H II regions in six southern spiral galaxies were observed using a combination of multiaperture masks and conventional long-slit spectrophotometry. The oxygen abundances derived from the multiaperture mask observations using the empirical abundance diagnostic R(sub 23) are shown to be consistent with those from long-slit spectra and generally show better reproducibility and object definition. Although the number of objects that can be observed simultaneously with this particular system is still quite limited compared with either imaging spectrophotometry or fiber-fed spectrographs, the spectral resolution offered and high throughput in the blue help make multiaperture spectrophotometry a competitive technique for increasing the sampling of H II regions in both radial distance and luminosity. There is still no clear trend of abundance gradient with either the galaxy's luminosity or its Hubble type, although the extrapolated central abundance does appear to correlate with galaxy luminosity/mass. In order to avoid difficulty in choosing an appropriate normalizing radius, we instead plot the oxygen abundance against the underlying I-band surface brightness at the radial distance of the H II region and confirm the existence of a local metallicity-surface brightness reltaionship within the disks of spiral galaxies. Although the simple closed-boc model of galaxy evolution predicts almost the right form of this relationship, a more realistic multizone model employing expnentially decreasing gas infall provides a more satisfactory fit to the observational data, provided the expected enriched gas return from dying low-mass stars shedding their envelopes at late epochs is properly taken into account. This same model, with a star formation law based upon self-regulating star formation in a three-dimensional disk (Dopita & Ryder

  15. Testing of Liquid Metal Components for Nuclear Surface Power Systems

    NASA Technical Reports Server (NTRS)

    Polzin, Kurt A.; Godfroy, Thomas J.; Pearson, J. Boise

    2010-01-01

    The Early Flight Fission Test Facility (EFF-TF) was established by the Marshall Space Flight Center (MSFC) to provide a capability for performing hardware-directed activities to support multiple in-space nuclear reactor concepts by using a non-nuclear test methodology. This includes fabrication and testing at both the module/component level and near prototypic reactor configurations. The EFF-TF is currently supporting an effort to develop an affordable fission surface power (AFSP) system that could be deployed on the Lunar surface. The AFSP system is presently based on a pumped liquid metal-cooled (Sodium-Potassium eutectic, NaK-78) reactor design. This design was derived from the only fission system that the United States has deployed for space operation, the Systems for Nuclear Auxiliary Power (SNAP) 10A reactor, which was launched in 1965. Two prototypical components recently tested at MSFC were a pair of Stirling power conversion units that would be used in a reactor system to convert heat to electricity, and an annular linear induction pump (ALIP) that uses travelling electromagnetic fields to pump the liquid metal coolant through the reactor loop. First ever tests were conducted at MSFC to determine baseline performance of a pair of 1 kW Stirling convertors using NaK as the hot side working fluid. A special test rig was designed and constructed and testing was conducted inside a vacuum chamber at MSFC. This test rig delivered pumped NaK for the hot end temperature to the Stirlings and water as the working fluid on the cold end temperature. These test were conducted through a hot end temperature range between 400 to 550C in increments of 50 C and a cold end temperature range from 30 to 70 C in 20 C increments. Piston amplitudes were varied from 6 to 1 1mm in .5 mm increments. A maximum of 2240 Watts electric was produced at the design point of 550 hot end, 40 C cold end with a piston amplitude of 10.5mm. This power level was reached at a gross thermal

  16. Effect of wear of bearing surfaces on elastohydrodynamic lubrication of metal-on-metal hip implants.

    PubMed

    Liu, F; Jin, Z M; Hirt, F; Rieker, C; Roberts, P; Grigoris, P

    2005-09-01

    The effect of geometry change of the bearing surfaces owing to wear on the elastohydrodynamic lubrication (EHL) of metal-on-metal (MOM) hip bearings has been investigated theoretically in the present study. A particular MOM Metasul bearing (Zimmer GmbH) was considered, and was tested in a hip simulator using diluted bovine serum. The geometry of the worn bearing surface was measured using a coordinate measuring machine (CMM) and was modelled theoretically on the assumption of spherical geometries determined from the maximum linear wear depth and the angle of the worn region. Both the CMM measurement and the theoretical calculation were directly incorporated into the elastohydrodynamic lubrication analysis. It was found that the geometry of the original machined bearing surfaces, particularly of the femoral head with its out-of-roundness, could lead to a large reduction in the predicted lubricant film thickness and an increase in pressure. However, these non-spherical deviations can be expected to be smoothed out quickly during the initial running-in period. For a given worn bearing surface, the predicted lubricant film thickness and pressure distribution, based on CMM measurement, were found to be in good overall agreement with those obtained with the theoretical model based on the maximum linear wear depth and the angle of the worn region. The gradual increase in linear wear during the running-in period resulted in an improvement in the conformity and consequently an increase in the predicted lubricant film thickness and a decrease in the pressure. For the Metasul bearing tested in an AMTI hip simulator, a maximum total linear wear depth of approximately 13 microm was measured after 1 million cycles and remained unchanged up to 5 million cycles. This resulted in a threefold increase in the predicted average lubricant film thickness. Consequently, it was possible for the Metasul bearing to achieve a fluid film lubrication regime during this period, and this was

  17. Ribosomal DNA (rDNA) identification of the culturable bacterial flora on monetary coinage from 17 currencies.

    PubMed

    Xu, Jiru; Moore, John E; Millar, B Cherie

    2005-03-01

    The aim of the investigation reported in this paper was to identify the bacterial microflora on monetary coinage from 17 countries by employment of polymerase chain reaction (PCR) sequenced-based molecular identification of rDNA from bacterial cultures. Silver, bronze, and other alloy coins (approximately 300 g) from 17 currencies were enriched individually by aerobic culturing in tryptone soya broth for 72 hours at 30 degrees C. Next, 20 microL of broth was inoculated onto Columbia blood agar supplemented with 5 percent volume-pervolume (v/v) defibrinated horse blood for 72 hours at 30 degrees C, and resulting colonies were purified by further subculture, as detailed above, for a further 72 hours. All colonies were identified by initial PCR amplification of a partial region of the 16S rDNA gene locus, which was then sequenced, and the sequence was aligned according to the BLASTn algorithm. Twenty-five isolates were obtained from the coinage; of these, 25 (100 percent) were Gram positive, and the most prevalent genus observed was Bacillus (B. megaterium, B. lentus, B. litoralis, B. subtilis, B. circulans and other Bacillus spp.), which accounted for 10 of 25 isolates (40 percent) and was isolated from 10 of 17 countries (58.8 percent). It was followed in prevalence by Staphylococcus spp. (Staph. aureus, Staph. epidermidis, Staph. hominis, Staph. schleiferi), which accounted for 7 of 25 isolates (28 percent) and were isolated from 7 of 17 countries (41.2 percent). Given the organisms identified in this study, it is not believed that monetary coinage presents any particular risk to public health. The authors support the principles of basic hygiene, however, in terms of proper handwashing and the avoidance of handling money when working with food or dressing wounds and skin lesions, In conclusion, the study demonstrated that money from 17 countries was contaminated by environmental Gram-positive flora, in particular Bacillus spp., and that the universal 16S r

  18. A broadened classical master equation approach for nonadiabatic dynamics at metal surfaces: Beyond the weak molecule-metal coupling limit.

    PubMed

    Dou, Wenjie; Subotnik, Joseph E

    2016-01-14

    A broadened classical master equation (BCME) is proposed for modeling nonadiabatic dynamics for molecules near metal surfaces over a wide range of parameter values and with arbitrary initial conditions. Compared with a standard classical master equation-which is valid in the limit of weak molecule-metal couplings-this BCME should be valid for both weak and strong molecule-metal couplings. (The BCME can be mapped to a Fokker-Planck equation that captures level broadening correctly.) Finally, our BCME can be solved with a simple surface hopping algorithm; numerical tests of equilibrium and dynamical observables look very promising.

  19. The effect of metal surface treatment on the shear bond strengths of base and noble metals bonded to enamel.

    PubMed

    Breeding, L C; Dixon, D L

    1996-10-01

    Adhesive resin luting agents provide a way for bonding metal surfaces to teeth through a combination of micromechanical retention to the rough metal surface and chemical adherence to metal oxides. The purpose of this study was to measure the effect of metal alloy surface treatments that would produce different textures and oxide layers on the shear bond strength of three alloys luted to etched enamel with one adhesive resin luting agent (Panavia). After a simulated porcelain firing sequence, high noble (Olympia), noble (Jelstar), and base metal (Rexillium III) alloy specimens were subjected to one of the following treatments: (1) sandblasting and simulated glazing, (2) simulated glazing only, (3) simulated glazing and sandblasting, or (4) simulated glazing, sandblasting, and tin plating. The specimens were bonded to extracted teeth and subjected to shear testing after water storage for 2 weeks, thermocycling for 500 cycles, and water storage for an additional 2 weeks. Data were analyzed with a two-way analysis of variance (alpha = 0.05). The base metal specimens and the tin-plated high noble and noble metal specimen groups exhibited similar mean shear bond strengths that were greater than the other groups. Those high noble and noble metal alloys sandblasted after simulated porcelain firing cycles and before the simulated glaze cycle exhibited nonsignificant increases in shear bond strengths compared with the groups that were either sandblasted after the simulated glaze cycle or not sandblasted at all.

  20. Rotating Molten Metallic Drops and Their Applications for Surface Tension Measurements

    NASA Technical Reports Server (NTRS)

    Rhim, W. K.; Ishikawa, T.

    1998-01-01

    Shapes and stability of rotating molten metal drops carrying net surface electric charges are experimentally investigated, and the feasibility of measureing surface tension based on drop rotation is examined.