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The temperature dependences of the composition of the outer monolayers of the surface of thermoemitters, namely, oxide, scandate, thoriated tungsten, and carbide cathodes, have been studied by the methods of low-energy ion and recoil atom scattering, Auger spectroscopy, and secondary ion mass spectroscopy. It has been established that the surfaces of oxide, scandate, and tungsten-thorium cathodes at operating temperatures contain a monoatomic film of active material (barium, thorium), which forms on the surface of the emitter when heated to operating temperature and dissolves in volume when the temperature drops to room temperature. As a result of activation, free barium accumulates in the volume of oxide crystals. It is shown that there is a slight increase in tantalum on the surface of tantalum carbide and it contains foreign electronegative adatoms (oxygen, chlorine, and sulfur) that cannot be removed at temperatures of 2500 K. [ABSTRACT FROM AUTHOR]

The article presents the results of a study of vacuum-arc coatings obtained by the sputtering of Ti–B–Si–Ni cathodes fabricated using self-propagating high-temperature synthesis with simultaneous pressing. The techniques for manufacturing cathodes of the indicated composition are characterized; the modernized HNV 6.6-I1 installation, the conditions and modes of coating deposition in an argon atmosphere and in a nitrogen + argon gas mixture in the ratio of 90/10 are described. To study the physical and mechanical properties of the resulting coatings, the hardness is measured at different loads on the indenter; the strength of adhesion to the base is assessed by the Rockwell method; the elemental composition of the cathodes and the (Ti–B–Si–Ni)N coating is determined using Auger spectroscopy, and the phase composition of the (Ti–B–Si–Ni)N coating is determined using X-ray phase analysis; a study of the properties of the coating (Ti–B–Si–Ni) is carried out by scratch testing. As a result of a comprehensive analysis of the results obtained, it is concluded that the high hardness of the (Ti–B–Si–Ni)N coating (more than 40 GPa) is due to its composition, which includes both nitrides and high-hardness titanium borides. The heterophase nature of the structure of this coating can serve as a contribution to the stressed state of the material. The coating has a graded-layer structure. The material contains a Ti–B–Si–Ni layer bound to the substrate and the main functional layer (Ti–B–Si–Ni)N. The coating has both a high hardness and sufficient strength of adhesion to the base (adhesion) determined by scratch testing. The combination of these properties makes the material promising for its practical application in the production of tools. [ABSTRACT FROM AUTHOR]

This paper reviews a procedure that allows for extracting primary photoelectron or Auger electron emissions from homogeneous isotropic samples. It is based on a quantitative dielectric description of the energy losses of swift electrons travelling nearby surfaces in presence of stationary positive charges. The theory behind the modeling of the electron energy losses, implemented in a freely available QUEELS-XPS software package, takes into account intrinsic and extrinsic effects affecting the electron transport. The procedure allows for interpretation of shake-up and multiplet structures on a quantitative basis. We outline the basic theory behind it and illustrate its capabilities with several case examples. Thus, we report on the angular dependence of the intrinsic and extrinsic Al 2s photoelectron emission from aluminum, the shake-up structure of the Ag 3d, Cu 2p, and Ce 3d photoelectron emission from silver, CuO and CeO2, respectively, and the quantification of the two-hole final states contributing to the L3M45M45 Auger electron emission of copper. These examples illustrate the procedure, that can be applied to any homogeneous isotropic material. [ABSTRACT FROM AUTHOR]

Oils and iron fines deposit on carbon steel during cold rolling and are removed by an electrolytic cleaning line (ECL). Sometimes localized contamination is observed on the ECL samples. No reliable tests are available for on-line measurement and the off-line tests demand samples with a large surface area. SKP addresses this issue effectively. SKP shows ∼390 mV potential difference between the clean and the uncleaned surface, with the cleaned surface potential being more positive. This indicates that the oil on the steel acts as a Lewis base, whereas the steel surface acts as a Lewis acid. Hence, the potential of the sample increases after cleaning. FTIR confirmed the absence of oil peaks on the cleaned samples. Deposition of an optimum thickness of the silicate layer is another important aspect of the ECL. It was measured by AES which displayed 2.3 nm of the silicate layer deposited on the cleaned steel surface. [ABSTRACT FROM AUTHOR]

The effect of changing the terminal functional group of C7 and C8 carboxylate species adsorbed on copper on the rate of tribochemical decomposition is investigated both in an ultrahigh vacuum tribometer and using an atomic force microscopy (AFM) tip, where the conditions are selected to provide similar normal stresses for both experiments. The carbon chains are terminated by alkyl, vinyl and acetylide groups, where the different chain lengths are selected to modify the orientation of the terminal π-orbitals. The pull-off forces measured by AFM are in accord with the calculated molecular structure but, despite this, the rates of tribochemical decomposition of all the adsorbed carboxylates are identical. However, the carbon is lost from the surface at different rates and this is ascribed to the different reactivities of the resulting carbonaceous species that are tribochemically produced at room temperature, but form thermally at ~ 650 K. This results in lower-energy barrier pathways, such as β-hydride elimination reactions, occurring preferentially compared to higher-activation-energy ones, such as coupling reactions. It is proposed that these rates are influenced by the ability of the terminal groups to access the copper surface and accounts for the relative reaction rates and the amount of carbon deposited onto the surface. [ABSTRACT FROM AUTHOR]

Composition, chemical structure, and dielectric characteristics of boron carbonitride films BCxNy prepared by chemical vapor deposition upon thermal and plasma activation of the initial gas mixture are studied. The dependence of elemental composition, dielectric constant, and resistivity of the films on synthesis conditions (type of the organoboron precursor, synthesis temperature, type and content of the additional gas) are determined by Auger electron spectroscopy and X-ray photoelectron spectroscopy. The dielectric constants of prepared films vary within 3.7-6.3 and their resistivities vary within 1012-1015 Ω·cm. The stability of dielectric properties of BCxNy films during their storage in air is studied for the first time. [ABSTRACT FROM AUTHOR]

Nickel composite coating reinforced with reduced graphene oxide is fabricated by pulse electrodeposition method from a surfactant‐free bath at different current densities. The reduction of graphene oxide is done by an ecofriendly method which uses chlorophyll (CHL) as the reducing agent. The CHL also acts as a stabilizer because of its amphiphilicity. Auger electron spectroscopy is used to study the surface morphology and characteristics of the deposited coatings. Nanoindentation is used to study the mechanical properties. Electrochemical techniques such as potentiodynamic polarization and electrochemical impedance spectroscopy are used to study the corrosion behavior in 3.5 wt% NaCl solution. The coatings are found to exhibit superior hardness, Young's modulus, and corrosion resistance when compared with the pure Ni coating. Hardness and corrosion resistance are found to improve almost tenfold at optimized condition. Scanning electron microscopy of the corroded surface of the coatings provides an insight into the corrosion process. [ABSTRACT FROM AUTHOR]

Using the methods of tunneling, infrared, X-ray photoelectron, Auger, and Raman spectroscopies, X-ray diffraction, and transmission electron microscopy, we study the structure and conductive properties of carbon films synthesized on various metal substrates (Al, Mo, Re, Ta, Ag, Cu, and Pt). The effect of the substrate material on the properties of the carbon film is studied. Based on non-empirical quantum-mechanical calculations, an analysis of the experimental vibrational spectra is carried out. The work function of the substrate material is concluded to depend on the length of the chain fragment. [ABSTRACT FROM AUTHOR]

Copyright of Sensor Electronics & Microsystems Technologies / Sensorna Elektronika i Microsystemni Tekhnologii is the property of I. I. Mechnikov Odessa National University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Abstract: The distribution of copper, carbon, and oxygen in the surface layers of steel 30KhGSN2A plates after the implantation of copper ions from a pulsed ion source with an accelerating voltage of 30 kV in a vacuum chamber with a residual gas pressure of 8 × 10-4 Pa is studied by Auger spectroscopy. The depth profile of copper in the surface layer has a maximum at a distance of ~90 nm from the plate surface. This profile is close to the depth distribution of implanted copper atoms in 30KhGSN2A steel under the same conditions that was simulated by the Monte Carlo method. The difference between the experimental and calculated profiles is caused by the fact that a 50-nm-thick carbon layer forms on the steel surface during implantation. In the revealed intermediate layer (50-120 nm), iron is partly in the oxidized state. Possible mechanisms of the influence of the structure of the surface layers that form during copper implantation into steel 30KhGSN2A plates on their tribological properties are considered. [ABSTRACT FROM AUTHOR]

Auger spectroscopy has not found widespread application in the geological sciences, largely because specimens are often non-conductors that charge under electron beams. However, it has proven to be useful for the characterization of sub-micrometer mineral grains in certain meteorites, where sample charging issues can be mitigated. We describe the development of analytical protocols for the measurement of presolar silicate grains using Auger spectroscopy and review how this technique has helped our understanding of the stellar origin and subsequent evolution of these grains. [ABSTRACT FROM PUBLISHER]

Ultrathin carbon films were grown on different types of metallic substrates. Free-standing foils of Cu and Ni were prepared by electroforming, and a pure Ni film was obtained by galvanic displacement on a Si wafer. Commercial foil of Ni 99.95% was used as a reference substrate. Carbon films were grown on these substrates by chemical vapour deposition in a CH4-H2 atmosphere. Obtained films were characterized by Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy, and ultraviolet photoemission spectroscopy. The XPS at grazing collection angle was used to determine the thickness of carbon films. Depending on the deposition parameters, the films of graphene or graphite were obtained on the different substrates. The uniformity of graphene and its distribution over the sample area were investigated from Raman data, optical images, and XPS chemical maps. The presence of graphene or graphite in the films was determined from the Raman spectra and Auger peak of C KVV. For this purpose, the D parameter, which is a fingerprint of carbon allotropes, was determined from C KVV spectra acquired by using X-rays and electron beam. A formation of an intermediate layer of metal hydroxide was revealed in the samples with graphene overlayer. [ABSTRACT FROM AUTHOR]

In this paper, we investigate the influence of temperature on the nickel grain boundary equilibrium segregation of sulfur and the resulting intergranular fracturing susceptibility. Auger electron spectroscopy has been used to study equilibrium segregation of sulfur to the grain boundaries of a metallic nickel, with a mass bulk content of 3.6ppm in sulfur. Samples were first annealed at adequate temperatures for sufficiently large equilibrium time, and then quenched in water at room temperature. The analysis carried out shows a significant increase of sulfur concentration in the grain boundary with decreasing temperature. However, the sulfur content in the grain boundary shows a drastic shrink at 700C. This can be interpreted by the formation of an aggregate sulfide compound in the area of the grain boundaries. At 650C, in situ brittle fracture becomes unworkable and only intragranular fractures are observed. Using the results obtained through the investigation of the grain boundaries by Auger spectroscopy, the standard segregation energy is estimated as . [ABSTRACT FROM AUTHOR]

Results of the investigation of multicomponent coating deposition on the metal substrate in the cathode part of a dense plasma focus device are presented. The features of the processes accompanying the coating are considered: evaporation of elements of chromium-manganese austenite 25Cr12Mn20W tube, which was located along the axis of the plasma focus PF-1000 chamber, under high temperature dense deuterium plasma and deposition of the elements on the model material in form of a copper arc. It is shown that, in the realized exposure mode (the power density of the plasma flow q = 10-10 W/cm in the zone of its impact on the tube and q = 10 W/cm in the region of interaction of the plasma with the copper substrate), the proposed method makes it possible to obtain a coating of submicron thickness on the substrate surface, which includes the evaporated elements of the steel tube. The combined action of powerful streams of fast deuterons and hot plasma in the central part of the copper arc was examined. The structural state, elemental composition, mechanical characteristics, and possible mechanisms for hardening of the deposited film coating are discussed. [ABSTRACT FROM AUTHOR]

AlN-SiC-YAlO composite materials with a high absorption of microwave frequency (27-65 dB/cm) produced by pressureless sintering of mixtures consisting of AlN(2H), YO, and SiC (6H) in 46, 4, 50 wt %, respectively, have been studied. The SiC components of the mixtures were used in sizes of 1, 5, and 50 μm. It has been shown that the resistivity of the developed materials depends essentially on the materials structures: sizes of SiC inclusions, distances between them, and state of the interfaces. It has been found that the increase of the SiC inclusions sizes in the material structure from 3 to 7 μm results in the decrease of the resistivity from 10 to 90 Ω·m, and at the decrease of the SiC inclusions sizes from 3 to 0.5 μm there forms a SiC uninterrupted skeleton, which also decreases the resistivity to 210 Ω·m. Thus, composite materials that contain 50 wt % SiC (inclusions sizes of 3 μm) are the most efficient in producing absorbers of microwave radiation. Interlayers of yttrium aluminum garnet, which are located at the SiC grains boundaries, prevent the forming of AlN(2H)-SiC(6H) solid solutions and thus, make it possible to keep high dielectric characteristics of a composite material based on aluminum nitride and afford a high absorption of a microwave radiation. [ABSTRACT FROM AUTHOR]

The corrosion behavior of nitride ceramics of different compositions, particularly AlN-TiN, 3AlN-TiN, AlN-3TiN, and TiAlN, has been studied in seawater (3% NaCl solution). The methods of potentiodynamic polarization curves as well as X-ray diffraction and Auger spectroscopy are employed. The AlN-TiN samples show the highest corrosion resistance. When anodic polarization of the samples increases to +1.20 V (in relation to their stationary potential -0.22 V), their surface becomes the most passive one, and the samples no more pass into the solution. In case of more positive potentials, very thin protective films form on the samples, representing a two-phase coating consisting of AlOOH and NaTiO. Other composite ceramics are not characterized by such exceptional stability: longer regions of active dissolution are observed on the anodic polarization curves for these ceramics. For the samples of comparatively corrosion-resistant 3AlN-TiN ceramics, two-phase corrosion products, AlOOH and Al(OH), are formed. The AlN-TiN ceramic composite is recommended as the most corrosion-resistant material for seawater applications. [ABSTRACT FROM AUTHOR]

We propose a facile and environmentally friendly method to prepare concentrated copper nanoparticles dispersion via reduction of aqueous copper(II) sulfate solution with ascorbic acid or glucose in the presence of gelatin as stabilizer. The so synthesized hydrosols have been examined using a set of physicochemical methods (ex situ and in situ) in order to determine the nanoparticles features. [ABSTRACT FROM AUTHOR]

The findings of an investigation into the impact of ions on the atomic state of the upper layer of He-Ne laser cathodes are presented. The research results are obtained using electron-probe microscopy, X-Ray photoelectron spectroscopy, and Auger spectroscopy, including the scanning mode. Changes in the surface compositions of the cathodes and active-element mirrors of lasers are revealed before and after tests. [ABSTRACT FROM AUTHOR]

Memristive properties of the pulsed laser deposited Pt/TiOx/TiO2/Pt heterostructures with different layer thicknesses are studied. It was found that the memristor device provides nonmonotonic dependence of the ratio of its resistance in low and high conductive states Roff/Ron on layers thickness. The maximum value of the ratio Roff/Ron = 200 is obtained when the thickness of both TiOx and TiO2 layers is 30 nm. The dependence of the stoichiometry index of deposited layers from their thicknesses is studied by means of Auger spectroscopy measurements. The nonmonotonic behaviour of the ratio Roff/Ron on layer thickness is discussed in terms of wide stoichiometry distribution through the amorphous TiOx/TiO2 structure. (© 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Copyright of Canadian Journal of Chemical Engineering is the property of Wiley-Blackwell and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Diamond-like carbon (DLC) coatings have been known for their low friction and high wear resistance for many years, but only in recent years have these coatings been used in mass-produced engines due to significant improvement in coating deposition techniques resulting in good adhesion on substrate materials. The interactions of these coatings with engine oils have been a focus for further research in recent years. In this investigation, the interactions of engine oil additives with five different DLC coatings containing two different doping elements were explored using a laboratory reciprocating rig under boundary lubrication condition. Two different contact geometries were investigated: a piston ring-on-liner and cylinder-on-flat to simulate piston ring and cylinder bore and cam and tappet applications. It was observed that DLC-coated piston rings offered lower friction coefficients and lower wear of the liner compared to commonly used Mo-NiCr-coated piston rings. However, the wear of the DLC-coated rings varied. The presence of lubricant additive–derived films could be observed on the wear surfaces of three of the DLC-coated surfaces irrespective of their doping element. In addition, the thickness of the lubricant additive–derived films on DLC-coated surfaces (a) was lower than that formed on ferrous materials and (b) depended on engine oil formulations. [ABSTRACT FROM AUTHOR]

The practical possibility of synthesizing micron-size corrosion-resistant powder materials based on lower and higher nitrides of the Fe-N system in the form of both a bulk composition and a 'core-shell' system was implemented at relatively low temperatures. Information on the elemental and chemical composition of iron nitrides was obtained using the methods of Auger electron spectroscopy and X-ray quantitative analysis. FeN and FeN phases were identified in the volume of microcrystals in the form of compositions with unreacted α-Fe without foreign impurities in the temperature range of 300-350°C. The highest mass concentration of the FeN phase was observed at 350°C and a nitriding time of 60 min (α-Fe, 14.70%; FeN, 24.50%; and FeN, 60.80%). Porous nanocoatings were synthesized on the surfaces of carbonyl iron microparticles at 165°C and a synthesis time of 420 min. This nanocoating has a thickness of ∼10-15 nm and, in the first approximation, corresponds to the ∼FeN compound. [ABSTRACT FROM AUTHOR]

While the field emission acts at the technical vacuum level conditions (10-5 Pa) and electrons emitted from cathode, the ion bombardment exists and continuously modifies the cathode surface. Using X-ray photoelectron spectroscopy (XPS) we studied the electronic structure of thin surface layer of artificial carbon-based materials (ACB) used as field emission cathodes (FEC). The research resulted in the spectra of the samples B-1300, B-1500, B-1900. After spectra processing features analysis shows the change in type of hybridization of the original material. This change is supported by three characteristic spectral features: asymmetry of the core levels spectrum lines change, the satellite structure transformation, Auger-line and modification. So the initial material had sp2 type of hybridization, the spectra show that in thin surface layer a new phase with sp3-hybridization exists and we can conclude formation of nanoclusters with diamond-phase in thin surface layer of cathode. (© 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

The surface and tribological chemistry of 2-propanol and borate esters, isopropoxy tetramethyl dioxaborolane (ITDB), and tetramethyl dioxaborolane (TDB) as gas-phase lubricants for copper surfaces are compared by measuring the friction coefficient and contact resistance in an ultrahigh vacuum tribometer. 2-propanol reacts on copper below room temperature to desorb primarily acetone and causes no friction reduction when used as a gas-phase lubricant. TDB decomposes to deposit BO species on the surface and produces an initial decrease in friction coefficient that is not sustained. ITDB, which reacts at room temperature to form a tetramethyl dioxaborolide species on the surface, results in an immediate and sustained decrease in friction coefficient when used as a gas-phase lubricant for copper. This indicates that the surface chemistry of the borate esters can be correlated with their tribological properties and illustrates the effect of replacing a hydrogen atom in TDB with a 2-propoxy group in ITDB on both the surface and tribological chemistry. Analysis of the species formed in the wear track after lubrication with ITDB reveals the presence of graphitic or diamond-like carbon and oxygen, and these elements are also found in the subsurface region of the sample. Rubbing the sample in vacuo after reacting with ITDB shows the removal of a boundary film where the coefficient remains constant and the subsequent removal of the subsurface layer in which the contact resistance rises to its original value. [ABSTRACT FROM AUTHOR]

The kinetics of the shear-induced surface-to-bulk transport of methyl thiolate species formed from dimethyl disulfide (DMDS) on a copper surface are explored. It is found that the loss of surface species as a function of the number of rubbing cycles can be modeled by assuming that the adsorbed layer penetrates the subsurface a distance of ~0.7 nm per scan. Adding wear to this model does not improve the fit to the experimental data providing an upper limit for the wear rate of ~0.06 nm/scan. This model is applied to analyzing the depth distribution of sulfur within the subsurface region as a function of the number of rubbing cycles, measured by Auger depth profiling when continually dosing the copper sample with DMDS. It is found that the shape of the experimental depth profile is in agreement with the model developed to analyze the surface-to-bulk transport kinetics of the adsorbed layer. However, the profiles are almost identical for surfaces that have been rubbed 130 and 360 times, so that the surface-to-bulk transport kinetics are self limiting. [ABSTRACT FROM AUTHOR]

X-ray photoelectron and Auger spectroscopy are used to investigate the chemical composition of BCN films synthesized by PECVD from different initial gas mixtures in the temperature range 473-723 K. Main principles and features of the film formation are found. It is shown that the chemical composition of BCN films significantly depends on the synthesis parameters, which enables targeted control of their physical properties. The obtained data are discussed. [ABSTRACT FROM AUTHOR]

Identification of intermediate and final products of the chemical reaction that produces nanodiamond particles is a key factor in understanding its mechanism. In this work different nanodiamond samples were studied before and after chemical cleaning by X-ray photoelectron and Auger spectroscopy. It was found that the chemical state of carbon atoms is the same before and after chemical cleaning. We find that the carbon atoms are sp3-bonded inside nanodiamond particles and have a new, unique chemical state on the surfaces. The latter differs significantly from sp2- and sp3-bonded carbon and can be figured as the valence band near the Fermi level being occupied by three electrons. [ABSTRACT FROM AUTHOR]

Results are reported from an experimental study of exciton-like two-hole states in nanoclusters of the narrow-band metals (Co, Ni, Cu) on highly oriented pyrolytic graphite HOPG(0001) surfaces. A technique is proposed for measuring long-lived two-hole states in the nanometer range based on observed features of the x-ray photoelectric and Auger spectra of nanoclusters. [ABSTRACT FROM AUTHOR]

Polarization curves and Auger spectroscopy are used to study the kinetics, formation mechanism, and layer-by-layer phase composition of oxide films resulting from the anodic oxidation of SiC-TiB-BC ceramics containing 10 wt.% and 40 wt.% TiB in 3% NaCl solution. It is shown that a two-layer oxide film forms in the former case (β-TiO is the lower layer and TiO the upper one) and a three-layer film forms in the latter case (nonstoichiometric β-TiO is the upper and lower layers and β-TiO the intermediate one). All ceramic samples, especially those with 10 wt.% TiB, have high corrosion resistance. [ABSTRACT FROM AUTHOR]

Over the past five decades, ultra high vacuum (uhv) techniques applied to well-defined single-crystal samples (the "surface science paradigm") have transformed our understanding of fundamental surface chemistry. To translate this success to the world of realistic heterogeneous catalysis, however, requires one seriously to address the fact that real heterogeneous catalysts usually operate under near-ambient or higher pressures. Nevertheless, the surface science paradigm can undoubtedly provide crucial insights into catalytic processes, so long as care is exercised in the design of experiments. Forging a secure link between two radically different pressure regimes is the major challenge, which we illustrate here with reference to the vitally important ammonia synthesis reaction, achieved industrially only under extremely high pressure. [ABSTRACT FROM AUTHOR]

Predictions from molecular dynamics (MD) simulations, that sliding at a metal-metal interface causes vortices in the near-surface region that transport atoms from the surface into the subsurface region, is tested experimentally. This is accomplished by rubbing a methyl thiolate overlayer grown on a clean copper foil by exposure to dimethyl disulfide at room temperature. Repeatedly rubbing a 1.27 × 10 m diameter pin over a thiolate-covered copper surface at an applied load of 0.44 N and sliding speed of 4 × 10 m/s in an ultrahigh vacuum tribometer, results in the removal of sulfur from the wear track as measured using spatially resolved Auger spectroscopy. Any remaining surface species, in particular, outside the wear track, are removed by argon ion bombardment. Since sulfur is more thermodynamically stable at the surface, heating the sample causes the sulfur to resegregate to the surface only inside the wear track, thereby directly confirming the predictions from MD simulations. [ABSTRACT FROM AUTHOR]

The charged state of the 3 d metal ions in layered cation-substituted disulfides CuCr1− xV xS2 was studied by X-ray photoelectron spectroscopy. An analysis of the energy positions and structure of the Cu2 p3/2 and Cr2 p3/2 X-ray photoelectron lines showed that the corresponding polycrystalline samples of CuCr1− xV xS2 contained mixed-valence chromium and copper ions. It was shown that the charged states of chromium and copper ions depended on the concentration of vanadium cations ( x). The presence of mixed-valence Cu1+ and Cu2+ ions in CuCr1− xV xS2 may be correlated with the crystal structure of the corresponding layered disulfides. [ABSTRACT FROM AUTHOR]

One-monolayer (ML) (thin) and 5-ML (thick) Si films were grown on the α-phase Si(111)√3 × √3R30°-Bi at a low substrate temperature of 200 °C. Si films have been studied in situ by reflection electron energy loss spectroscopy (REELS) and Auger electron spectroscopy, as a function of the electron beam incidence angle α and low-energy electron diffraction (LEED), as well as ex situ by grazing incidence X-ray diffraction (GIXRD). Scanning tunneling microscopy (STM), and scanning tunneling spectroscopy (STS) were also reported. The REELS spectra, taken at the Si K absorption edge (~1.840 KeV), reveal the presence of two distinct loss structures attributed to transitions 1s→π* and 1s→σ* according to their intensity dependence on α, attesting to the sp2-like hybridization of the silicon valence orbitals in both thin and thick Si films. The synthesis of a silicon allotrope on the α-phase of Si(111)√3 × √3R30°-Bi substrate was demonstrated by LEED patterns and GIXRD that discloses the presence of a Si stack of 3.099 (3) Å and a √3 × √3 unit cell of 6.474 Å, typically seen for multilayer silicene. STM and STS measurements corroborated the findings. These measurements provided a platform for the new √3 × √3R30° Si allotrope on a Si(111)√3 × √3 R30°-Bi template, paving the way for realizing topological insulator heterostructures from different two-dimensional materials, Bi and Si. [ABSTRACT FROM AUTHOR]

Environmental regulations have called for a reduction of phosphorus content in engine oils in recent years. The anti-wear additive zinc dialkyl dithiophosphate (ZDDP), which is also an antioxidant, is one of the most important components of engine oil additives. ZDDP is a major source of phosphorus. One way to reduce phosphorus levels is to replace ZDDP with new environmentally friendly antiwear agents that have similar or superior wear performance compared to ZDDP. Another way to address the environmental issue is to reduce the amount of ZDDP in engine oils. At the same time, it is necessary to increase the efficiency of ZDDP by finding optimum conditions that would result in improved antiwear performance. The antiwear mechanism of ZDDP involves its degradation thermally and tribologically, leading to the formation of an antiwear film that consists of polyphosphates and sulphides. The structure of the antiwear film is almost similar in both types of degradation. But the breakdown efficiency of ZDDP is diminished by the parallel reaction of ZDDP with other additives, as well as the antagonistic effects of these additives. The new fluorinated ZDDP complex developed has shown better wear performance compared to ZDDP. This would allow the possibility of further reduction of phosphorus in engine oils compared to current levels. In this paper we study the interaction of ZDDP and fluorinated ZDDP with alkylated diphenylamine. The impact of antioxidant on wear performance was examined using a ballon-cylinder tribometer. The interactions between ZDDP and the fluorinated ZDDP with the antioxidant were studied using NMRand the surface of the tribofilm was examined using SEM, TEM, and Auger spectroscopy. [ABSTRACT FROM AUTHOR]

From specific heat measurements of Ta + Ti alloyed Bronze Route multifilamentary Nb3 Sn wires, a wide, nearly symmetric overall distribution of Tc can be determined. This is apparently in contradiction with the almost linear decrease of the Sn content towards the centre of the A15 filaments, which suggests a rather sharp drop of the T~ distribution at the higher Tc side. In order to find an explanation to this problem, high resolution Auger spectroscopy measurements have been performed in filament bundles located at various positions of the wire cross section. It was found that the degree of reaction as well as the Sn gradient in each filament show substantial differences depending on its location, either in an innermost or outermost bundle. A model was established, assuming three different filament groups: 1) outer bundles: fully reacted filaments, almost constant Sn content, 2) intermediate bundles: partially reacted, shallow Sn gradient, and 3) inner bundles: partially reacted, steep Sn gradient. Summing together the contribution of the three groups, a total Sn distribution for the wire was obtained. Based on the relationship between Tc and the Sn content in alloyed Nb3Sn, a T. distribution can be found which corresponds to that one measured by specific heat. [ABSTRACT FROM AUTHOR]

AlGaN/GaN heterostructures passivated by SiO2/Si3N4 and SiNx/Si3N4 bilayers were characterized electrically by capacitance-voltage measurements and chemically by Auger microscopy chemical in-depth profiling. The 2-dimensional electron gas density was estimated from C-V curves and the electronic quality of the bilayers was evaluated from C-V hysteresis. Detailed variations of Auger peaks, in particular for oxygen, silicon, nitrogen, and carbon, versus argon ion sputtering time were registered. The electronic properties of these two structures were compared with each other and to their chemistry. [ABSTRACT FROM AUTHOR]

Effect of bicarbonate ions on the copper passivity and its local breakdown is studied by cyclic voltammetry, Auger spectroscopy, x-ray photoelectron spectroscopy, and scanning electron microscopy. Comparing data for solutions with various sodium bicarbonate concentrations shows copper to undergo pitting in 0.02 M NaHCO3, whereas it remains stably passive in 0.10 M NaHCO3. Independent studies suggest that carbonates play a protective role in stabilization of the oxide-hydroxide passive film on copper. [ABSTRACT FROM AUTHOR]

The friction coefficients of thin KCl films deposited onto clean iron in ultrahigh vacuum are measured using a tungsten carbide tip. A rapid decrease is found in the friction coefficient from ∼ 2 for clean iron to 0.27 ± 0.03 after the deposition of ∼40 Å of KCl. Based on previous contact resistance measurements, this was proposed to be due to the completion of the first layer of KCl. The first-layer KCl coverage was measured by adsorbing deuterium onto an iron surface partially covered by KCl, where deuterium selectively adsorbs onto the iron. This revealed that the first monolayer is complete after the deposition of ∼40 Å of KCl and that the first-layer KCl film coverage ΘKCl (1) is given by ΘKCl (1) = 1 - exp(-0.39±0.02 t), where t is the film thickness. XPS data suggest that heating a KCl film to ∼550 K causes it to wet the surface. This leads to decreases in the friction coefficients for thin KCl films in accord with the idea that friction is reduced by the first monolayer of KCl on iron. Temperature-programmed desorption data indicate that KCl in the first monolayer is ∼5 kJ/mol more stable than the multilayer consistent with the wetting behavior. Finally, the kinetic data are analyzed to suggest that the first-layer film is ∼2.6 Å thick. [ABSTRACT FROM AUTHOR]

The temperature dependence of the rate constants for the dissolution of gold in thiourea solutions was determined. The activation energies calculated suggest that the rate of gold dissolution is diffusion-controlled at 5-22 °C but is kinetically-controlled at 25-60 °C ( Ea = 42.83 kJ/mol). Auger spectroscopy was used to study the composition of the surface adsorption layers and a mechanism for the passivation of the reactive surface during the gold dissolution process was proposed. [ABSTRACT FROM AUTHOR]

The effect of temperature in rolling contact performance of a hot isostatically pressed (HIP) silicon nitride ball material with a linear perfluoropolyalkylether (PFPAE) was studied using a ball-on-rod type rolling contact fatigue tester. The test temperature ranged from ambient to 343 °C for a period of 24 h at a stress of 5.5 GPa using thin dense chrome (TDC)-coated T-15 bearing races. The lubricant and its decomposition products, specifically acid fluoride and acids, attacked Si3N4 balls at all test temperatures resulting in corrosion pitting. The presence of metal fluoride on all the Si3N4, transferred from the races, was detected by X-ray photon spectroscopy (XPS). The thickness of the oxide layer formed on the balls, as determined by Auger electron spectroscopy (AES) increased with temperature. The changes in physical properties of post-test lubricant showed that the lubricant was stable at temperatures up to 288 °C. The change in viscosity was constant up to 288 °C and with a significant change above 288 °C. The FTIR analysis of 316 and 343 °C post-test lubricant showed the presence of carboxylic acid. The total acid number (TAN) increased linearly up to 288 °C and accelerated at 316 and 343 °C. The study indicates that the use of Si3N4 balls with a linear PFPAE results in an incompetent tribo system. [ABSTRACT FROM AUTHOR]

Molecular beam studies carried out in ultrahigh vacuum show that dimethyl disulfide reacts with initially clean iron to evolve methane. The reaction is proposed to proceed via a methyl thiolate intermediate. Reaction ceases at ∼600 K, an effect that is proposed to be due to the surface being blocked by an overlayer of sulfur and carbon. Reaction recommences above ∼950 K as sulfur diffuses into the iron. The activation energy for the film-forming reaction is 52.5±2.1 kcal/mol, in good agreement with the activation energy for the growth of FeS films from dimethyl disulfide at higher pressures measured using a microbalance. A depth profile of the film grown in ultrahigh vacuum shows that the sulfur-containing film grows on a Fe+C underlayer. Similar molecular beam experiments with diethyl disulfide suggest the formation of an intermediate ethyl thiolate species which decomposes via a β-hydride elimination reaction to evolve ethylene. The activation energy for film growth, in this case, is 60±2.4 kcal/mol. The results of tribological experiments using a pin and v-block apparatus are consistent with FeS forming the anti-seizure film. [ABSTRACT FROM AUTHOR]

Dc molecular-beam methods are used to examine the reactivity of carbon tetrachloride with oxide films grown on iron in ultrahigh vacuum. The incident CCl4 beam flux is sufficiently low that the nature of the surface oxide is dictated by the annealing temperature allowing the reactivity of Fe2O3, Fe3O4 and FeO films to be examined. Carbon tetrachloride reacts rapidly with Fe2O3 and reaction with Fe3O4 commences at ∼620 K to evolve CO. The activation energy for this process is 20.6±1.0 kcal/mol. CCl4 reacts with FeO above ∼790 K, also to evolve CO, and the activation energy for this reaction is 5.7±0.4 kcal/mol. X-ray photoelectron spectroscopy shows the formation of a halide after reaction at 900 K. These results are in accord with film-growth kinetics measured using a microbalance at high pressures, where it was found that it was not necessary to remove the oxide layer prior to reaction. This contrasts with the behavior of sulfur-containing molecules, where the oxide layer had to be removed before a film would grow. This effect may contribute to the additive synergies commonly found in extreme-pressure lubricant additives where one of the roles of the chloride may be to reduce the oxide layer. [ABSTRACT FROM AUTHOR]

Active catalysts for metathesis of alkenes, hydrodesulfurization, and hydrogenation can be prepared by exposing a high surface area alumina support to molybdenum hexacarbonyl at room temperature. This strategy is mimicked in ultrahigh vacuum by adsorbing molybdenum hexacarbonyl onto an ultrathin hydroxylated alumina film grown onto a Mo(100) substrate. In contrast to results found on high surface area, no Mo(CO)6 is found to adsorb on alumina at 300 K, and significant molybdenum deposition is only found by heating the sample to above 670 K. Alternatively, molybdenum hexacarbonyl adsorbs on alumina when cooled to 80 K. In this case the majority of the carbonyl desorbs intact and temperature programmed desorption and X ray photoelectron spectroscopy indicate that ∼2% of a monolayer of the carbonyls undergoes decarbonylation. Auger and X ray photoelectron spectroscopy measurements reveal that molybdenum carbide (MoC) is deposited onto the alumina surface heated to 700 K forming a monolayer after an exposure of ∼50 L. This layer is reduced to the metal by heating to ∼1500 K by reaction with the alumina substrate to evolve CO and form metallic molybdenum. The carbide can be reformed by heating the metal covered alumina sample in ethylene at 900 K, and the carbide can once again be reduced to the metal by heating to 1500 K. This process can be repeated so that the carbide can be regrown by reaction with ethylene and reduced by annealing in vacuo to 1500 K. Subcarbonyl species are detected after adsorbing Mo(CO)6 on hydroxylated alumina at 80 K as the sample is heated to ∼200 K. At higher temperatures, the molybdenum is oxidized to an approximately 4+ oxidation state and deposits primarily oxalate species on the surface. The adsorbed oxalates thermally decompose at ∼300 K to evolve CO to form surface formates. These are stable to ∼560 K and react to evolve CO at this temperature. It is also found that the extent of decarbonylation depends on the degree of alumina hydroxylation so that heating hydroxylated alumina to 900 K, which removes ∼50% of the surface hydroxyls, decreases the both CO desorption yield and the oxalate coverage by 50%. [ABSTRACT FROM AUTHOR]

In bench tribology tests, the influence of lubricant decomposition products on the lubricated system and on lubricant performance are often overlooked, primarily because testing is performed in vented, or open, systems. However, the lubricant in a gas turbine engine might be expected to more closely follow the principles of interaction that are found in unvented, or closed, systems. Results reported here comparing vented and unvented bearing housings in rolling contact fatigue (RCF) tests with a linear perfluoropolyalkylether (PFPAE) lubricant and VIM-VAR M50 steel at 316°C and a stress of 4.8 GPa clearly show that significantly more wear, corrosion, and fluid breakdown occur in the closed system than in the open system. Under these conditions, PFPAEs catalytically decompose to corrosive products. These corrosive products are partially vented in the open system, but retained in the closed system, causing more extensive corrosion of bearing materials, and significantly affecting the lubricant's tribological performance. Post test lubricant was analyzed for viscosity, acid number, and metals to assess changes in the lubricant's physical and chemical properties. Changes were more severe in the closed system. The nuclear magnetic resonance (NMR) and Fourier transform infrared (FTIR) spectra also showed significantly more carboxylic acid buildup in the stressed fluid from the closed system. The films formed in the tribojunction were analyzed using X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). Organic films formed in the open system reduced wear while inorganic films formed in the closed system resulted in higher wear. Consequently, we conclude that more attention needs to be given to the effect of decomposition products during bench type tribological testing of high temperature lubricants. [ABSTRACT FROM AUTHOR]

The thermal decomposition of carbon tetrachloride on clean iron was studied in ultrahigh vacuum using molecular beam strategies, where it is found that carbon tetrachloride thermally decomposes on the surface to deposit iron and carbon with exactly identical kinetics as found at high pressures. No gas phase products are detected and the activation energy for the reaction (14.2 ± 0.5 kcal/mol) is in good agreement with the value measured at high pressures. Little carbon is detected on the surface using Auger spectroscopy following reaction and it is found that this diffuses into the surface much faster when formed from CCl4 than from CH2Cl2. This effect is ascribed to the effect of co adsorbed chlorine on the adsorbed carbon, which is proposed to decrease the activation energy for diffusion into the bulk of the sample. This effect explains the increased tendency for carbon tetrachloride to form carbides under extreme pressure tribological conditions. [ABSTRACT FROM AUTHOR]

A study of the adsorption of oxygen on steel at room temperature has been performed in an ultra-high-vacuum system with oxygen in the pressure range from 10 to 10 Torr. Ellipsometry, surface potential difference, and Auger spectroscopy were the surface techniques used. The surface of the steel was cleaned by Cs and Ar bombardment. The mechanism of the adsorption process is postulated to involve adsorption of molecular oxygen, followed by dissociation and chemisorption of atomic oxygen to form one monolayer. Further adsorption on top of this monolayer is associated with a place-exchange process to produce multilayers of oxide. [ABSTRACT FROM AUTHOR]

It is widely held that most oxidation in thermally sprayed coatings occurs on the surface of the droplet after it has flattened. Evidence in this paper suggests that, for the conditions studied here, oxidation of the top surface of flattened droplets is not the dominant oxidation mechanism. In this study, a mild steel wire (AISI 1025) was sprayed using a high-velocity oxy-fuel (HVOF) torch onto copper and aluminum substrates. Ion milling and Auger spectroscopy were used to examine the distribution of oxides within individual splats. Conventional metallographic analysis was also used to study oxide distributions within coatings that were sprayed under the same conditions. An analytical model for oxidation of the exposed surface of a splat is presented. Based on literature data, the model assumes that diffusion of iron through a solid FeO layer is the rate limiting factor in forming the oxide on the top surface of a splat. An FeO layer only a few nanometers thick is predicted to form on the splat surface as it cools. However, experimental evidence shows that the oxide layers are typically 100× thicker than the predicted value. These thick oxide layers are not always observed on the top surface of a splat. Indeed, in some instances the oxide layer is on the bottom, and the metal is on the top. The observed oxide distributions are more consistently explained if most of the oxide forms before the droplets impact the substrate. [ABSTRACT FROM AUTHOR]

The formation of TaSi in the Si-PtSi-Ta and Si-Ta systems has been studied using Auger spectroscopy, x-ray diffraction and electron diffraction techniques. The reaction of tantalum with PtSi was observed by Sinha, et al. to take place with high temperature (800°-900°c) annealing of thin film systems consisting of Si-PtSi-Ta-W. In the present investigation, it is shown that tantalum reacts with PtSi at approximately 600°C to form a mixture of TaSi and TaSi and predominantly TaSi at 785°C. Platinum is displaced at the refractory metal (Ta)-PtSi interface, whereupon the more stable refractory metal-silicide is formed. The displaced platinum reacts further with the excess silicon which diffuses from the Si-PtSi interface. The Si-PtSi-Ta reaction is similar to the Si-PtSi-W reaction. However, unlike tungsten which migrates very little in the Si-PtSi-W system, tantalum appears to interdiffuse with the PtSi at temperatures as low as 600°C. In the case of the Si-Ta couple, TaSi forms at approximately 750°C as determined by transmission electron microscopy (TEM) measurements. The kinetics of TaSi formation at the Si-Ta interface are compared to that which takes place at the PtSi-Ta interface to determine the influence of the PtSi layer. Silicide formation was not observed in SiO-Ta specimens. after anneals up to 800°c. At 750°C TaO formed as observed by electron diffraction. [ABSTRACT FROM AUTHOR]

The concurrent application of the SEM, AES, X-ray diffractometry and Rutherford Backscattering (RBS) techniques to Au/refractory metallizations is analyzed with respect to the study of thin film interdiffusion, intermetallic formation, microcracking and oxidation phenomena. The SEM in the backscatter electron image mode was used for resolution of intermetallic compounds and interdiffusion products, while AES and RBS analyses were used to obtain depth-composition profiles. The metallizations studied were Ta/Pt/Ta/Au and W/Au. The combination of Ta/Pt/Ta and Ti/Pt have been shown to be effective barriers to gold-silicon interdiffusion. Defects in the tungsten barrier were found to result in silicon migration to the front surface and gold migration toward the substrate at temperatures between 550°C-700°C . The diffusion constants for Au-Ta and Au-Pt interdiffusion have been determined from the AES data. [ABSTRACT FROM AUTHOR]

Experimental requirements for a successful application of sputtering techniques for depth profiling are summarized. Evidence is given for the depth resolution expected from the sputtering process. Principles for the evaluation of the concentration-depth relation in SIMS and AES are discussed. Examples of both techniques demonstrate present possibilities for depth analysis. [ABSTRACT FROM AUTHOR]