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BACKGROUND Orthopedic implant-related infection remains one of the most serious complications after orthopedic surgery. In recent years, there has been an increased scientific interest to improve prevention and treatment strategies. However, many of these strategies have focused on chemical measures. AIM To analyze the effect of alternating current electrical fields on bacterial adherence to titanium surfaces. METHODS Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) were exposed to 6.5 V electrical currents at different frequencies: 0.5 Hz, 0.1 Hz, and 0.05 Hz. After exposure, a bacterial count was then performed and compared to the control model. Other variables registered included the presence of electrocoagulation of the medium, electrode oxidation and/or corrosion, and changes in pH of the medium. RESULTS The most effective electrical model for reducing S. aureus adhesion was 6.5 V alternating current at 0.05 Hz achieving a 90% adhesion reduction rate. For E. coli, the 0.05 Hz frequency model also showed the most effective results with a 53% adhesion reduction rate, although these were significantly lower than S. aureus. Notable adhesion reduction rates were observed for S. aureus and E.coli in the studied conditions. However, the presence of electrode oxidation makes us presume these conditions are not optimal for in vivo use. CONCLUSION Although our findings suggest electrical currents may be useful in preventing bacterial adhesion to metal surfaces, further research using other electrical conditions must be examined to consider their use for in vivo trials., Peer Reviewed, Postprint (published version)

Ferroalloys are one of the most important raw materials widely used in the steelmaking processes. Depending on the cleanliness of used ferroalloys, they can be an inevitable source of impurities and nonmetallic inclusions (NMIs) in steelmaking products. Herein, the inclusions in five different industrial ferroalloys (FeTi, FeMo, FeW, MnN, and FeCrN) are investigated. This is done using 2D investigations on polished cross sections of ferroalloy samples and using 3D investigations of NMIs on film filters and metal surfaces after electrolytic extraction (EE) using scanning electron microscopy in combination with energy-dispersive spectroscopy (SEM-EDS). Moreover, the characteristics of the main types of inclusions presented on film filters and metal surfaces after EE are compared and their possible transformations in Al-killed steel are evaluated. The results show that the main inclusions are more likely the oxidization products of the reductant and some unreduced ore during the ferroalloy production process. The 3D investigations of inclusions on metal surfaces after extraction are found to be very useful in detection and evaluation of larger-sized inclusions. Overall, this study helps to better understand the impurities in different ferroalloys and their possible effect on the steel cleanliness., QC 20220502

Electrocatalytic denitrification is a promising technology for removing NOx species (NO3 - , NO2 - and NO). For NOx electroreduction (NOxRR), there is a desire for understanding the catalytic parameters that control the product distribution. Here, we elucidate selectivity and activity of catalyst for NOxRR. At low potential we classify metals by the binding of ?NO versus ?H. Analogous to classifying CO2 reduction by CO vs?H, Cu is able to bind?NO while not binding ?H giving rise to a selective NH3 formation. Besides being selective, Cu is active for the reaction found by an activity-volcano. For metals that does not bind NO the reaction stops at NO, similar to CO2-to-CO. At potential above 0.3 V vs RHE, we speculate a low barrier for N coupling with NO causing N2O formation. The work provide a clear strategy for selectivity and aims to inspire future research on NOxRR.

Los nanomateriales y especialmente los denominados materiales nanoestructurados, esto es organizados a la escala nanométrica, incluyen a los materiales híbridos como ejemplo paradigmático de nanotecnología emergente con incidencia en sectores críticos como salud, alimentación, energía, medio ambiente, transporte o vivienda. El ensamblado a nivel atómico-molecular, o sea a la escala nanométrica, de varios componentes de distinta naturaleza (orgánica e inorgánica, por ejemplo) permite disponer de materiales híbridos dotados de propiedades sinérgicas y provistos de características predeterminadas. Este es el caso de los materiales compuestos (composites) que a la escala nanométrica se conocen como nanocomposites, un verdadero tópico asociado a los materiales de vanguardia en los que una matriz polimérica contiene nanopartículas altamente dispersas confiriendo propiedades estructurales y funcionales de gran interés aplicativo en áreas de la ingeniería, arquitectura, biomedicina, farmacología, agricultura, etc. Los procesos preparativos de los materiales híbridos órganoinorgánicos tienen lugar a temperaturas moderadas, permitiendo que alguno de los componentes sea de origen biológico preservando a veces propiedades ligadas a los seres vivos. Este es el caso de los denominados materiales biohíbridos y bionanocomposites, de los que la Naturaleza ofrece ejemplos como huesos, marfil, nácar, etc. Aplicando métodos de biomimetismo se pueden producir artificialmente estos materiales biohíbridos de interés, por ejemplo, en nuevas aplicaciones biomédicas.

Inert metal surfaces present more chances of hosting organic intact radicals than other substrates, but large amounts of delocalized electronic states favor charge transfer and thus spin quenching. Lowering the molecule-substrate interaction is a usual strategy to stabilize radicals on surfaces. In some works, thin insulating layers were introduced to provide a controllable degree of electronic decoupling. Recently, retinoid molecules adsorbed on gold have been manipulated with a scanning tunneling microscope (STM) to exhibit a localized spin, but calculations failed to find a radical derivative of the molecule on the surface. Now the formation of a neutral radical spatially localized in a tilted and lifted cyclic end of the molecule is presented. An allene moiety provokes a perpendicular tilt of the cyclic end relative to the rest of the conjugated chain, thus localizing the spin of the dehydrogenated allene in its lifted subpart. DFT calculations and STM manipulations give support to the proposed mechanism.

An appropriate corrosion protection is required for transport and storage of high-quality goods and semi-finished parts made from metals. The application of volatile corrosion inhibitors (VCI) as a means of temporary corrosion protection is based on the release of corrosion inhibitors from films, papers, diffusers or oils to the gaseous phase. By adsorption on the metal surface, the inhibitors prevent the degradation of the primary oxide layer and hence impede corrosion. In principle, the anticorrosive effect is independent of the part geometry, because the protected surfaces do not need direct contact with the VCI material. Also, the VCI method does not require costly cleaning of parts prior to further use after transport and storage. The EXCOR jar test is a common method to examine the efficiency of VCI. A metallic sample and a VCI material are exposed in a jar. After conditioning in dry and humid atmosphere, corrosive stress is applied to the sample. To clarify the VCI's mechanism of action, the test steps, their duration and the type of inhibitors were varied. Thus, the operating principle of VCI during the test was identified. The acquired knowledge enables to understand and tailor the corrosion protection by VCI in service.

The development of 2D nanomaterial coatings across metal surfaces is a challenge due to the mismatch between the metal microstructure and the nanoscale materials. The naturally occurring thin oxidative layer present across all metal surfaces, may lead to low adherence and connectivity. In this paper, graphene/titania/Titanium hybrid films were for the first time fabricated by a single step chemical vapour deposition process across Titanium foils. The presence of graphene as a dopant was found to enhance the photocatalytic performance of the final products, applied to the degradation of organic molecules and to lead to Schottky-like junction formation at the metal/oxide interface. These Schottky junctions, where vacancies are present across the titania material due to the graphene doping and where Ti3+ ions are predominantly located, yield enhanced catalytic performance. The highest degradation rate was found to be 9.66 × 10-6 min-1, achieved by the sample grown at 700 °C for 5 min, which was 62% higher than the sample just treated at that temperature without graphene growth. This work provides evidence that graphene may be grown across pure Titanium metal and opens new avenues in biomedical devices design, tribological or separation applications.

Due to its beneficial corrosion resistance, stainless steel is widely used in, e.g., biomedical applications, as surfaces in food contact, and for products intended to come into skin contact. Low levels of metals can be released from the stainless steel surface into solution, even for these highly corrosion resistant alloys. This needs to be considered in risk assessment and management. This review aims to compile the different metal release mechanisms that are relevant for stainless steel when used in different biological settings. These mechanisms include corrosion-induced metal release, dissolution of the surface oxide, friction-induced metal release, and their combinations. The influence of important physicochemical surface properties, different organic species and proteins in solution, and of biofilm formation on corrosion-induced metal release is discussed. Chemical and electrochemical dissolution mechanisms of the surface oxides of stainless steel are presented with a focus on protonation, complexation/ligand-induced dissolution, and reductive dissolution by applying a perspective on surface adsorption of complexing or reducing ligands and proteins. The influence of alloy composition, microstructure, route of manufacture, and surface finish on the metal release process is furthermore discussed as well as the chemical speciation of released metals. Typical metal release patterns are summarized., QC 20151116

In this work, carbon steel (CS) covered with bronze coating was treated by silane coupling agents with an aim to improve surface adhesion between metal and rubber blend. As we know the silane coupling agents offer the ability to form a durable bond between organic and inorganic materials. Through hydrolysis reaction R- silyl group can form a chemical bond with the inorganic surface. Two different chemical properties of materials provide high adhesive strength or improvement of the adhesion strength 1,2. The surfaces characteristics were analyzed by XPS, FTIR, and Contact angle measurements. Surface morphology of bronze surface treated by APS was investigated by AFM., In this work, carbon steel (CS) covered with bronze coating was treated by silane coupling agents with an aim to improve surface adhesion between metal and rubber blend. As we know the silane coupling agents offer the ability to form a durable bond between organic and inorganic materials. Through hydrolysis reaction R- silyl group can form a chemical bond with the inorganic surface. Two different chemical properties of materials provide high adhesive strength or improvement of the adhesion strength 1,2. The surfaces characteristics were analyzed by XPS, FTIR, and Contact angle measurements. Surface morphology of bronze surface treated by APS was investigated by AFM.

We study the effect of electron and phonon degrees of freedom on the relaxation dynamics of adsorption processes in gas-surface systems by using ab initio molecular dynamics that incorporates an electronic friction force (AIMDEF). As representative cases we have chosen three systems with different adsorption energies and adsorbate-to-surface atom mass ratios: H on Pd(1 0 0), N on Ag(1 1 1), and on Fe(1 1 0). We show, through inspection of the total energies and trajectories of the hot adsorbates on the surface, that electron–hole (e–h) pair excitations dominate relaxation of the light gas species, while the phonon channel is dominant for the heavy species. In the latter case e–h pairs become more important at the final thermalization stages.

We present microwave-frequency NbTiN resonators on silicon, systematically achieving internal quality factors above 1?M in the quantum regime. We use two techniques to reduce losses associated with two-level systems: an additional substrate surface treatment prior to NbTiN deposition to optimize the metal-substrate interface and deep reactive-ion etching of the substrate to displace the substrate-vacuum interfaces away from high electric fields. The temperature and power dependence of resonator behavior indicate that two-level systems still contribute significantly to energy dissipation, suggesting that more interface optimization could further improve performance., QN/Quantum Nanoscience, Applied Sciences

Angle- and energy-loss-resolved distributions of helium atoms grazingly scattered from a Ag(110) surface along low indexed crystallographic directions are investigated considering impact energies in the few keV range. Final projectile distributions are evaluated within a semi-classical formalism that includes dissipative effects due to electron-hole excitations through a friction force. For mono-energetic beams impinging along the [11¯0],[11¯2] and [001] directions, the model predicts the presence of multiple peak structures in energy-loss spectra. Such structures provide detailed information about the trajectory-dependent energy loss. However, when the experimental dispersion of the incident beam is taken into account, these energy-loss peaks are completely washed out, giving rise to a smooth energy-loss distribution, in fairly good agreement with available experimental data.

The interaction of alkali atoms with metal surfaces is reviewed. The peculiar electronic configuration of such atoms, with only one valence electron participating in the bond formation, suggested simple pictures to describe their interaction with a metal surface. But it was early evident that the adsorption properties depend on many aspects, related to the electronic structure of constituents, leading, for example, to different degrees of ionicity/covalency of the alkali atom-metal bond. Sophisticated theoretical modeling tried to shed light on this aspect. The spectral properties are the ultimate features in determining how the systems interact with each other. In this review the electronic and spectral properties are discussed focusing on different theoretical representations of the physical system and on their consequences. Surface projected energy gaps of the substrate as well as the substrate continuous spectrum are key aspects in determining the nature of the interaction and bonding with alkali adsorbates. © 2013 Elsevier Ltd. All rights reserved.

Nonadiabatic energy transfer from the translational motion (T) of a molecule impinging on metal surface to the metal's electrons may determine whether the molecule can lose enough energy to adsorb or react. Although it is thus relevant to heterogeneous catalysis, little is known about the strength of the coupling of T to electron hole pair (ehp) excitation. We present adiabatic ab initio molecular dynamics (AIMD) predictions of the scattering of 5 eV H-atoms from Cu and Au surfaces. Calculations of angularly resolved scattering reveal experimentally realizable conditions where only about 2% of the incidence energy is lost to the metal's phonons. Under these conditions, measurements of the translational energy loss should be able to determine the magnitude of any additional energy loss due to ehp excitation, information that is very valuable to the development of accurate theoretical descriptions of T→ehp coupling. © 2013 American Chemical Society.

Coupling of Rayleigh waves propagating along two metal surfaces separated by a narrow fluid channel is predicted and experimentally observed. Although the coupling through a fluid (water) is weak, a strong synchronization in propagation of Rayleigh waves even for the metals with sufficiently high elastic contrast (brass and aluminum) is observed. Dispersion equation for two polarizations of the coupled Rayleigh waves is derived and experimentally confirmed. Excitation of coupled Rayleigh waves in a channel of finite length leads to anomalously low transmission of acoustic energy at discrete set of resonant frequencies. This effect may find useful applications in the design of acoustic metamaterial screens and reflectors. (C) 2012 Acoustical Society of America. [http://dx.doi.org/10.1121/1.4744939]

This paper was published in OPTICS EXPRESS and is made available as an electronic reprint with the permission of OSA. The paper can be found at the following URL on the OSA website: http://dx.doi.org/10.1364/OE.19.007664. Systematic or multiple reproduction or distribution to multiple locations via electronic or other means is prohibited and is subject to penalties under law, [EN] In this work, we demonstrate experimentally the use of an array of gold nanodisks on functionalized silicon for chemosensing purposes. The metallic nanostructures are designed to display a very strong plasmonic resonance in the infrared regime, which results in highly sensitive sensing. Unlike usual experiments which are based on the functionalization of the metal surface, we functionalized here the silicon substrate. This silicon surface was modified chemically by buildup of an organosilane self-assembled monolayer (SAM) containing isocyanate as functional group. These groups allow for an easy surface regeneration by simple heating, thanks to the thermally reversible interaction isocyanate-analyte, which allows the cyclic use of the sensor. The technique showed a high sensitivity to surface binding events in gas and allowed the surface regeneration by heating of the sensor at 150°C. A relative wavelength shift ¿¿max/¿0 = 0.027 was obtained when the saturation level was reached. © 2011 Optical Society of America.

The non-covalent synthesis of coordination compounds and networks provides promising avenues towards metal-containing supermolecules and nanostructured materials with ultimate feature definition. An important factor for their further development, and their integration and exploitation in nanoscale functional systems, is the capability to prepare or organize them at well-defined substrates or templated environments. Supra-molecular engineering on atomistically controlled surfaces has been propelled by the direct insight into low-dimensional coordination systems provided by scanning tunneling microscopy observations. Here we discuss the principles of surface-confined supramolecular coordination chemistry, emphasizing self-assembly protocols conducted on surface atomic lattices employing metal centers to direct the organization of molecular ligands and the template-induced organization of prefabricated metallosupramolecular species. The presented exemplary molecular-level studies elucidate the arrangement of organic adsorbates and transition metal adatoms on low-index metal and graphite surfaces. They reveal the interplay between molecule-adatom, intermolecular, and adsorbate-substrate interactions, which need to be balanced for the fabrication of low-dimensional nanostructures. The control and understanding of both the nature of metal-ligand interactions and the resulting supramolecular organization on solid surfaces is decisive for the design of advanced architectures with concomitant functions. The realized metallosupramolecular compounds and arrays combine the properties of their constituent metal ions and organic ligands, and feature versatile structural characteristics as well as attractive functional aspects: their redox, magnetic, spin-state, and electronic transitions.

7 p., 3 figuras, We present it ab initio calculations of the electronic energy loss of charged particles moving outside a magnesium surface, from a realistic description of the one-electron band structure and a full treatment of the dynamical electronic response of valence electrons. Our results indicate that the finite width of the plasmon resonance, which is mainly due to the presence of band-structure effects, strongly modifies the asymptotic behaviour of the energy loss at large distances from the surface. This effect is relevant for the understanding of the interaction between charged particles and the internal surface of microcapillaries.

25 p., 9 figuras, Exact-exchange self-consistent calculations of the Kohn-Sham potential, surface energy, and work function of jellium slabs are reported in the framework of the optimized effective potential (OEP) scheme of density functional theory. In the vacuum side of the jellium surface and at a distance z that is larger than the slab thickness, the exchange-only Kohn-Sham potential is found to be imagelike (similar to-e(2)/z) but with a coefficient that differs from that of the classical image potential V-im(z)=-e(2)/4z. The three OEP contributions to the surface energy (kinetic, electrostatic, and exchange) are found to oscillate as a function of the slab thickness, as occurs in the case of the corresponding calculations based on the use of single-particle orbitals and energies obtained in the local-density approximation (LDA). The OEP work function presents large quantum size effects that are absent in the LDA and which reflect the intrinsic derivative discontinuity of the exact Kohn-Sham potential.

The goal of this project was to use DNA and protein as templates to assemble nanoparticles and functional molecules for photonic and electronic applications such as plasmon-enhanced fluorescence and surface-enhanced Raman scattering (SERS) (Fig. 1). Towards this goal, we have utilized both genetic and materials engineering tools. We have followed the molecular biomimetic approach in the assembly of nanoparticles. We have developed protocols using involving biological attachment of nanoparticles and quantum dots onto engineered surface-binding polypeptides (GEPI), and have used directed assembly of nanoparticles and/or functional molecular units.

For bare metal stents the in-stent restenosis was a serious problem for about 25 - 35% of the patients and this spurred the medical device companies to come up with a solution. Drug-eluting stents are designed to deliver a drug locally from a polymeric coating to reduce tissue in growth and reduce restenosis to less then 8% of the treated patients. Development of novel materials and structures for drug delivery systems is still very actual topic. In the present work plasma immersion ion implantation (PIII) using helium or argon plasmas has been employed for the nanostructures formation on metal surfaces with a view to their applications for metal-based drug-eluting stents. A multi-layer pore system on stent surfaces in the range from nanoscale to microscale sizes is desired for drug loading and controlling the rate of elution of therapeutic agents. Recently we have investigate the formation of nanostructures on stainless steel surfaces by PIII at different gases (He, Ar), ion energies (between 5 – 35 keV) and ion fluences (> 1e18 at/cm2). The surface topography and structure of the implanted materials were analysed by scanning electron microscopy and atomic force microscopy. The phase and element compositions were examined by grazing incidence X-ray diffraction analysis, auger electron spectroscopy, and elastic recoil detection analysis. Variety of nanostructures as well as their characteristics (e.g. size, distribution, degree of interconnection) can be controlled by varying the implantation parameters. The results of these studies have demonstrated that PIII is a promising technique for the surface topography modification of stainless steel for cardiovascular application.

The negative refraction of surface waves on a structured metal surface is proposed and demonstrated. Sub-wavelength imaging of a point diploe source through a slab structure is also shown., QC 20141113

The structure, bonding and chemistry of water and hydroxyl on metal surfaces are presented. Synchrotron based x-ray photoelectron- and x-ray absorption spectroscopy along with density functional theory calculations mainly form the basis of the results. Conditions span the temperature range 35 - 520 K and pressures from ultra-high vacuum (~10 fAtm) to near ambient pressures (~1 mAtm). The results provide, e.g, new insights on the importance of hydrogen bonding for surface chemical kinetics. Water adsorbs intact on the Pt(111), Ru(001) and Cu(110) surfaces at low temperatures forming 2-dimensional wetting layers where bonding to the metal (M) mainly occurs via H2O-M and M-HOH bonds. Observed isotope differences in structure and kinetics for H2O and D2O adsorption on Ru(001) are due to qualitatively different surface chemistries. D2O desorbs intact but H2O dissociates in kinetic competition with desorption similar to the D2O/Cu(110) system. The intact water layers are very sensitive to x-ray and electron induced damage. The mixed H2O:OH phase on Ru(001) consists of stripe-like structures 4 to 6 Ru lattice parameters wide where OH decorates the edges of the stripes. On Pt(111), two different long-range ordered mixed H2O:OH structures are found to be inter-related by geometric distortions originating from the asymmetric H-bond donor-acceptor properties of OH towards H2O. Water adsorption on Cu(110) was studied at near ambient conditions and compared to Cu(111). Whereas Cu(111) remains clean, Cu(110) holds significant amounts of water in a mixed H2O:OH layer. The difference is explained by the differing activation barriers for water dissociation, leading to the presence of OH groups on Cu(110) which lowers the desorption kinetics of water by orders of magnitude due to the formation of strong H2O-OH bonds. By lowering the activation barrier for water dissociation on Cu(111) by pre-adsorbing atomic O, generating adsorbed OH, similar results to those on Cu(110) are obtained.

We report an ab initio study of electron–phonon interactions on the Be(0 0 0 1) surface. The calculations based on density-functional theory were carried out using a linear response approach in the plane-wave pseudopotential representation. The phonon-induced contribution to excited hole (electron) lifetime broadening is calculated for the zone center surface state. The obtained results show a rather strong momentum dependence.

The role that occupied d bands play in the inelastic lifetime of bulk and surface states in Ag is investigated from the knowledge of the quasiparticle self-energy. In the case of bulk electrons, sp bands are taken to be free-electron-like. For surface states, the surface band structure of sp states is described with the use of a realistic one-dimensional Hamiltonian. The presence of occupied d states is considered in both cases by introducing a polarizable background. We obtain inelastic lifetimes of bulk electrons that are in good agreement with first-principles band-structure calculations. Our surface-state lifetime calculations indicate that the agreement with measured lifetimes of both crystal-induced and image-potential-induced surface states on Ag(100) and Ag(111) is considerably improved when the screening of d electrons is taken into account.

We present first-principles calculations of electron-electron scattering rates of low-energy electrons in Au. Our full band-structure calculations indicate that a major contribution from occupied d states participating in the screening of electron-electron interactions yields lifetimes of electrons in Au with energies of 1.0-3.0 eV above the Fermi level that are larger than those of electrons in a free-electron gas by a factor of similar to 4.5. This prediction is in agreement with a recent experimental study of ultrafast electron dynamics in Au(111) films [J. Cao er al., Phys. Rev. B 58, 10 948 (1998)], where electron transport has been shown to play a minor role in the measured lifetimes of hot electrons in this material.

Silver cluster ions, Agx+ (x = 1-16), have been produced by fast atom bombardment of silver foil and silver salts in the external ion source of a Fourier transform ion cyclotron resonance mass spectrometer. Ion formation and collision-induced dissociation are discussed in relation to ion stabilities. Reactions of Agx+, x = 1-5, were studied with a variety of small molecules. Reactivity is dominated by adduct formation and silver atom displacement, which is dependent on cluster size. Contrasting reactivity was observed between Ag+ and A92-+ with 2-propanol, 2methyl-2-propanol and 2-methylpropane. Silver cluster ions, Mass spectrometry.

Phase I demonstrated that ion beam microtexturing of metal surfaces enhances heat transfer under three conditions: (1) thermal radiation emission at relatively high temperatures, (2) forced convection, and (3) nucleate boiling. Features were too small to significantly affect heat transfer under non-flowing constant phase conditions. For nucleate boiling, combining microtexture with large scale structures, and after optimizing the texturing process, it should be possible to achieve a composite enhancement better than 20 times the nucleate- boiling heat transfer from a smooth surface. Ion texturing processes produce rugged broadband light absorbers, completely black from the visible to long wavelength IR. At higher temperature ranges, enhanced radiation adds significantly to total heat transferred. Thus, heat pipes, capillaries, and higher temperature radiators would all perform better with microtextured surfaces.

This report summarizes work accomplished in the following task areas for the duration of this contract: a) The development of the Laser Melt/Particle Injection Process as a means to form sound, wear-resistant surfaces on soft metallic substrates; b) The research and development of powder metallurgy processes to further the understanding of particle atomization and to evaluate novel material production; and c) The characterization and testing of high performance metallic, ceramics and composite materials. Keywords: Laser processing, Powder metallurgy, Ceramics, Composite materials, Fracture mechanics.

The phenomena of non-linear junctions formed by contacting metal surfaces was investigated and a method to characterize these junctions is described. Normally linear components, such as points of contact, can become nonlinear elements. These can occur in coupling hardware of coaxial transmission lines, in flanged joints of wave guides and in other waveguide components that are bolted together. Chemical compounds build up on metal contact surfaces exposed to the atmosphere. The compounds, oxides and sulphides for example, are semiconductive and tend to increase contact resistance. They have a non-linear current-voltage characteristic that can be used to characterize Metal-Oxide- Metal junctions by non-linear measurements. When a pure sinusoidal current flows through a component (point of contact) the voltage across it is distorted by any nonlinearities present. The distorted voltage can be considered the sum of a fundamental frequency voltage and a number of voltages at harmonic frequencies. The magnitude of these harmonic voltages can serve as a measure of the nonlinearity present in the contact. For convenience, the third harmonic is usually chosen since it has the largest magnitude and therefore is easiest to measure., in French.

The principal task of this program was to develop a better understanding of: (1) the mechanisms of the growth of passive films on metal surfaces, (2) the role of space charge in determining the properties of the film, and (3) passivity breakdown phenomena. Experimental data for the ac impedance and passivity breakdown properties of passive films on nickel are presented in Sections 2 and 3. Also a theoretical development of the point defect model is presented in Section 4. A comparison between the theoretical and experimental data for the growth of passive films on nickel and iron is included. In addition, the role of minor alloying elements (such as molybdenum) on pitting and passivity breakdown is considered theoretically, and the model is compared with experimental data for 18% Cr ferritic stainless steel. The results of this study indicate that the point defect model although at present in a crude state of development, is a reasonable first-approximation theory for explaining some of the basic phenomna related to the growth and breakdown of anodic passive films on metal surfaces. On the basis of data developed in this program it is recommended that further experiments be conducted to further refine the model. Keywords: Pitting potentials, Passivity, Single crystal nickel, Polycrystalline nickel, Point defect model, and Space-charge.

An image field theory of surface enhanced Raman spectroscopy is used to study the dependence of Raman intensities on light frequency, nature of adsorbate and metal, electrode potential, scattering angle and light polarization. Although the image field enhancement (IFE) theory is at best a crude approximation to the true enhancement mechanism, it does find quite reasonable agreement between the IFE predictions and most existing experimental results.

The use of transmission infrared spectroscopy to investigate the chemisorption of CO and an electronic analog to CO is described. (Author)

The catalytic activity of transition metal surfaces can be altered significantly by the deposition of carbon adlayers. In the case of nickel surfaces, several catalytic processes are enhanced. For the case of tungsten, a reconstruction occurs and the resultant surface activity is associated with both structural and electronic changes induced by the deposition of carbon. Recent experimental studies on transition metal carbides and carburized transition metals have suggested that the carbon, either present in the bulk or exposed at the surface, affects the adsorption properties of simple gaseous adsorbates.

The design of a dual-band half-wave-plate mirror for a two-axis beam scan mirror antenna is described. The solution for design parameters is given for perfect 90 polarization rotation at a given aspect angle for each of the two bands. The process for optimizing the design for the full desired range of aspect is described. Practical fabrication considerations are discussed along with inclusion of capacitive susceptance of a protective covering in the design theory. Calculated performance is compared with measurements of mirror samples.

Li K., Xiao F., Lu F., Liu D., Alameh K., Xu A. (2014). Compact plasmonic dichroic splitting with high splitting ratio based on a cascaded-grating structure. Journal of the Optical Society of America B: Optical Physics, 31(2), 387-392. Available here

SCOPUS: ch.b, info:eu-repo/semantics/inPress

SCOPUS: ch.b, info:eu-repo/semantics/inPress

The adsorption and charge transfer dynamics of the organic molecule bi-isonicotinic acid (4,4′-dicarboxy-2,2′-bipyridine) on single crystal Ag(111) has been studied using synchrotron radiation-based photoemission, x-ray absorption and resonant core spectroscopies. Measurements for multilayer and monolayer coverage are used to determine the nature of the molecule-surface interactions and the molecular orientation. An experimental density of states for the monolayer with respect to the underlying metal surface is obtained by combining x-ray absorption spectroscopy at the N 1s edge and valence photoemission to measure the unoccupied and occupied valence states, respectively. This shows that the lowest unoccupied molecular orbital in the core-excited state lies energetically below the Fermi level of the surface allowing charge transfer from the metal into this orbital. Resonant photoelectron spectroscopy was used to probe this charge transfer in the context of super-spectator and super-Auger electron transitions. The results presented provide a novel interpretation of resonant core-level spectroscopy to explore ultra-fast charge transfer between an adsorbed organic molecule and a metal surface through the observation of electrons from the metal surface playing a direct role in the core-hole decay of the core-excited molecule.

Charge transfer interactions between C60 and the metal surfaces of Ag(111), Cu(111), Au(111) and Pt(111) have been studied using synchrotron-based photoemission, resonant photoemission and X-ray absorption spectroscopies. By placing the X-ray absorption and valence band spectra on a common binding energy scale, the energetic overlap of the unoccupied molecular orbitals with the density of states of the underlying metal surface have been assessed in the context of possible charge transfer pathways. Resonant photoemission and resonant Auger data, measuring the valence region as a function of photon energy for C60 adsorbed on Au(111) reveals three constant high kinetic energy features associated with Auger-like core-hole decay involving an electron transferred from the surface to the LUMO of the molecule and electrons from the three highest occupied molecular orbitals, respectively and in the presence of ultra-fast charge transfer of the originally photoexcited molecule to the surface. Data for the C60/Ag(111) surface reveals an additional Auger-like feature arising from a core-hole decay process involving more than one electron transferred from the surface into the LUMO. An analysis of the relative abundance of these core-hole decay channels estimates that on average 2.4 $\pm$ 0.3 electrons are transferred from the Ag(111) surface into the LUMO. A core-hole clock analysis has also been applied to assess the charge transfer coupling in the other direction, from the molecule to the Au(111) and Ag(111) surfaces. Resonant photoemission and resonant Auger data for C60 molecules adsorbed on the Pt(111) and Cu(111) surfaces are shown to exhibit no super-Auger features, which is attributed to the strong modification of the unoccupied molecular orbitals arising from stronger chemical coupling of the molecule to the surface.