State Of Elements Research Articles

X-ray photoelectron spectroscopy of the surface of solid electrolyte La0.88Sr0.12Ga0.82Mg0.18O3-α

The composition and chemical state of elements on the surface of solid oxygen-conducting electrolyte La0.88Sr0.12Ga0.82Mg0.18O3 – α is studied by x-ray photoelectron spectroscopy before and after annealing it at 973 K in a CO2 atmosphere. Products of interaction between doped lanthanum gallate and CO2 are localized in a surface layer 8–10 nm thick. The annealing does not lead to the formation of chemical carbon compounds with metals on the electrolyte surface. Surface layers of the electrolyte both in the initial state and after the annealing are rich in strontium oxide and contain some lanthanum hydroxide.

X-ray photoelectron spectroscopy of chemically deposited amorphous and crystalline Ni-B coatings

The chemical state of elements and the composition of surface and bulk layers of Ni–B coatings with the volume concentration of boron of 3.7 and 27.1 at. % obtained by electroless catalytic reduction are studied with x-ray photoelectron spectroscopy combined with layer-by-layer profile analysis. Up to 90% of nickel and 80% of boron are shown to be reduced on the surface of the coatings. The effect of the conditions of heat treatment in a vacuum and in air on the composition of the surface layer is analyzed. The original nonuniformity of the in-depth distribution of the elements is found to be most of all affected by heating in air at a temperature of 700°C that provides the surface formation of a B2O3 oxide layer containing no nickel. A stabilized composition of the alloys is observed at a depth of 10 to 60 nm depending on the conditions of heat treatment.

A study of the tribological behaviour of dialkyldithiophosphate esters as additives in rape seed oil

AbstractZinc dialkyldithiophosphates (ZDDP) cannot be used as additives in biodegradable lubricants because of their zinc content. In investigating substitutes for ZDDP, dialkyldithiophosphate esters have been synthesised, and their tribological behaviour as additives in rape seed oil has been evaluated using a four‐ball friction and wear tester and compared with that of ZDDP. The results show that these additives have better antiwear properties and load‐carrying capacity than rape seed oil alone. The morphologies and the elemental chemical states on the worn surfaces of the lubricated steel balls of the tester were examined using X‐ray photoelectron spectroscopy and scanning electron microscopy. The tribological mechanism is discussed on the basis of the experimental results.

XAFS in a single macrophage cell

In this paper, a novel approach using XAFS will be introduced for the study of the problem of cytotoxicity of metal ions. A micro beam from a SR source was used to measure the time-dependent distributions and chemical states of elements in mouse macrophages that were cultured in metallic solutions of different concentration. It is revealed that the concentrations and distributions of calcium, zinc and potassium in a single cell are closely related to the uptake of the metal. Using XAFS analysis, it is shown that metal elements absorbed by the cell interact with the cell and that the chemical state of the metal is changed.

The tribological behaviors of various metallic cations in tapping of a titanium alloy

In this paper, various metallic cations, including Na +, K +, Ca 2+ and Ba 2+, were introduced into water-based lubricating additives. Their tribological behaviors were investigated by the tapping test of a Ti-6Al-4V alloy. Among them, Ba-containing compound showed the best lubricating performance. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were employed to characterize the surface morphology and chemical states of elements, respectively. It was found that the worn surface consisted of multiple oxides, which implies that tribooxidation predominated during the frictional process under aqueous lubrication. Furthermore, barium titanate (BaTiO 3) could be detected on the tapped surface, the existence of which was proposed to be responsible for its corresponding performance.

Influence of ionic species on phase formation in ion mixing of carbon films on tungsten

Carbon films were deposited by r.f. magnetron sputtering on tungsten substrates followed by irradiating processes with nitrogen and argon ions. Microanalyses were used to obtain information on the phase, composition and chemical states of elements in the samples. It is found that Ar + ion irradiation did not lead to the formation of tungsten-carbide, while nitrogen ions bombardment can induce formation of WC x , and at the same time, can react with tungsten to form the WN phase. With alternating Ar + and nitrogen ions, the carbon films on tungsten substrate were transformed into tungsten-carbide.

Synthesis and characterization of a cobalt(III) complex with 1-( d-3-mercapto-2-methylpropionyl)- l-proline

The reaction of CoCl 2 with 1-( d-3-mercapto-2-methylpropionyl)- l-proline (L or captopril) yields a new nanocrystalline complex with general formula [CoL 2(OH)] 2. The complex has been characterised with infrared (IR) and ultra-violet visible (UV-vis) spectroscopies, magnetic measurements, X-ray photoelectron spectroscopy (XPS), and wide angle X-ray scattering (WAXS). XPS analyses is a valuable tool for studying the chemical composition and the chemical state of elements at the surface of solids whereas WAXS provides information on the short range order. A model is proposed for the binding of the complex and its structure: the Co(III) ion is bonded with a pseudo-octahedral configuration. Captopril molecules are coordinated via mercapto group and amidic CO group to Co(III) ions: two S atoms are bridging bonded between two Co(III) ions. The OH − ion completes the coordination around the Co(III).

Study of the tribological behavior of sulfurized fatty acids as additives in rapeseed oil

Odorless sulfurized fatty acids, sulfurized octadecanoic acid (SOA) and sulfurized docosanoic acid (SDA), were synthesized. The tribological behavior of the synthesized compounds as additives in rapeseed oil was evaluated and compared with octadecanoic acid using four-ball friction and wear testers. The morphologies and elemental chemical states on the worn surfaces of the lubricated GCr15 steel were investigated by means of X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). As the results, both SOA and SDA as additives in rapeseed oil show improved extreme pressure properties and friction-reducing behavior as compared with the rapeseed oil alone. They show better antiwear and extreme pressure properties than octadecanoic acid additive at relatively higher load. The differences in the tribological behavior of octadecanoic acid and SOA and SDA are attributed to their different action mechanisms therein. That is, octadecanoic acid functions by forming adsorption film alone while the two sulfurized fatty acids function by forming adsorption film and tribochemical reaction film during the friction process.

Synchrotron-based impurity mapping

Studies were performed on metal impurity precipitates in silicon using synchrotron-based X-rays. The elemental distribution and chemical state of metal impurities were measured by using synchrotron-based X-ray fluorescence (μ-XRF) and X-ray absorption spectroscopy (μ-XAS), both with a 1–2 μm 2 spatial resolution. With these systems we have identified preferred precipitation sites for metal impurities in silicon and we have correlated poor solar cell performance with metal impurity distributions. Furthermore, we have studied the dissolution rate of metal precipitates as a function of thermal treatment and we have analyzed the chemical state of metal precipitates in silicon. Discussions of metal precipitate stability are presented in regards to the chemical state and material improvement.

The tribological behaviors of copper-coated graphite filled PTFE composites

Polytetrafluoroethylene (PTFE) composites filled with different fillers and various filler proportions were made by compression molding. The powders of graphite, copper, copper-coated graphite (CCG), and copper-mixed graphite (CMG) were selected as the fillers. The tribological behaviors of composites in sliding against a stainless steel ring were evaluated on an MM-200 friction and wear tester. The morphologies and element chemical states of the worn composite surfaces were examined with scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS), respectively. It was found that the CCG particles prepared by chemical replacement method were characterized by loose and uniform covering of graphite particles by many tiny copper particles. The preferential transfer of graphite onto the surfaces of PTFE powders during the mixing process could be prevented by copper coating method, which was beneficial to further improving the wear resistance of composites. XPS analysis showed that no tribological reaction occurred during the friction process of PTFE sliding against stainless steel ring, but there was radical -CF 3 on the worn surfaces of PTFE composites, its generation mechanism and effect on the tribological behaviors of PTFE composites still need further study.

The effect of nitrogen ion implantation on tungsten surfaces

X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) were used to study the phase, composition and chemical states of elements at the tungsten surface. The measurement results indicate that nitrogen-containing phase of tungsten were formed by nitrogen ion implantation (energy 40 keV, implantation doses of 4×10 17, 8×10 17 and 1.6×10 18 ions/cm 2). The formation of the W x (O,N) and WN in the surface layer occurred as a result of nitrogen ion irradiation. A decrease in concentration of W x (O,N) is observed with increasing N + while that WN increases. Due to residual oxygen in the chamber WO 3 still exists at the surface of the specimen.

Microanalysis of post-irradiation of ions into carbon films on tungsten substrates

Abstract Carbon films were prepared by radio-frequency magnetron sputtering on tungsten substrates. The effect of post-irradiation (40 keV, 4×10 17 ions cm −2 ) with active nitrogen ions and inert argon ions was studied. The results show that combined irradiation with these two kinds ions can transform the carbon film into a carbide film due to induced mixing effects. X-ray diffraction and X-ray photoelectron spectroscopy were used to obtain information on the phases, composition and chemical states of elements at the specimen surface.

XPS study of polycrystalline and epitaxial FeTaN films deposited by d.c. reactive magnetron sputtering

Thin films of FeTaN have been investigated as potential head materials for several years. However, little information related to its chemical characteristics can be found in the literature, therefore polycrystalline and epitaxial FeTaN films were synthesized by d.c. reactive magnetron sputtering. Follow-up annealing was performed on some of the thin films under vacuum conditions. The chemical compositions and elemental chemical states of both kinds of thin films were investigated by x-ray photoelectron spectroscopy. It is shown that the nitrogen content in the films can be changed and easily controlled by varying the nitrogen gas flow rates during the deposition process. There are no large chemical shifts in the binding energies of Ta 4f, Fe 2p and N Is between polycrystalline and epitaxial films. No chemical compounds among Fe, Ta and N were formed in as-deposited or even in vacuum-annealed thin films. However, a chemical shift of Ta 4f from its atomic state was found. In addition, relatively large contents of carbon and oxygen inside the films were noticed. The existing chemical states, sources and possible effects of nitrogen, carbon and oxygen on the magnetic properties were studied and discussed.

X-ray Photoelectron Spectroscopy Analysis of Solid-Phase Reactions Using 3-Brominated Wang Resin

There is even more interest in the development of the solid-phase synthetic approaches to small molecules, particularly those which embrace heteroatom-containing molecules, for the purpose of medicinal and agricultural chemistry.1 Many heteroatom-containing molecules exhibit a broad range of biological activities for antiviral, antibacterial, antifungal, and antihypertensive drugs, as well as others.2 The major impediment in the solid-phase synthesis is the lack of analytical techniques for identifying the products and particularly for monitoring the progress of the reactions. As part of our continuing interest in the development of new solid-phase synthetic methods,3 we were looking for a new analytical method for monitoring the reaction and for identifying the product still bound to the polymer. Although there are a few techniques known for direct monitoring of samples still bound to resins, namely IR,4 NMR,5 and mass spectroscopy,6 we still need a new analytical method.7 X-ray photoelectron spectroscopy (XPS) has been widely used to acquire qualitative as well as detailed quantitative information about the composition and structure of organic and polymeric materials.8 As an analytical tool for organic and polymeric materials, XPS is known to have several advantages: It is a semiquantitative technique with a high surface sensitivity and is capable of identifying all elements except H and He. Also, XPS provides information about chemical states of elements.8 Since the most popular solid supports, such as the Wang and Merrifield resins, are mainly comprised of carbon and oxygen atoms and the concentration of the reacting site is very low (1-2 mmol per gram of resin), a simple XPS analysis of these polymers will only provide a limited piece of information.9 However, we envisioned that if we insert a suitable heteroatom as an internal standard (a marker) in the polymer, then we might be able to monitor around the Figure 1. X-ray photoelectron survey spectra for resins 1, 3, 5, and 6. The elements in the polymer-bound compounds can be readily identified by determining the binding energies of the photoelectron peaks. © Copyright 1999 by the American Chemical Society

A study of Ni3Al coating on carbon steel surface via the SHS casting route

Abstract A nickel aluminide (Ni3Al) coating on a carbon steel surface was fabricated by the self-propagating high-temperature synthesis (SHS) casting route. Coating phases were determined by using X-ray diffraction (XRD). The microstructure of the coating and bonding interface between the substrate and the coating, and the distribution of elements adjacent to the interface, were analyzed by using electron probe microanalysis (EPMA). The microhardness of the coating was measured. The tribological properties of the coating at different elevated temperatures were investigated and the worn surfaces at different temperatures were analyzed by EPMA. The elemental chemical state of the worn surface was determined by using X-ray photoelectron spectroscopy (XPS). The results show that the coating was composed of Ni3Al phase, and that its microstructure was dense and pure. Elements had diffused mutually at both sides of the interface and a metallurgical bonding interface was formed. The heat of the reaction coarsened the grain size of the substrate near the interface. The hardness of the coating is higher than that of the substrate. Wear loss and friction coefficient of the coating vary with the testing temperature. The coating had a good resistance to oxidation at elevated temperature. Oxidation of the coating occurred as a result of friction at the temperature of 873 K. The mechanisms of combustion synthesis of Ni3Al coatings on carbon steel substrates are discussed in detail. It is pointed out that the combustion temperature and the wettability between the product of the reaction and the substrate are significant to obtain the coating.

X-ray Spectro-Microscopy and Micro-Spectroscopy in the 2100 eV to 12000 eV Region (Invited)

ABSTRACTAn x-ray microprobe beamline was recently developed and commissioned at the Center for Advanced Microstructures and Devices (CAMD), Louisiana State University. It achieves a moderate horizontal and vertical focal spot size of 18.8 µm × 7.0 µm (σ), respectively. The beamline and end-station are designed and optimized to perform (i) spatially-resolved x-ray fluorescence spectroscopy (spectro-microscopy) using the broad intense spectrum of the white synchrotron radiation, and (ii) spatially-resolved x-ray absorption spectroscopy (micro-spectroscopy) in the energy region of 2100eV to 12000 eV. These dual capabilities enable K-edge measurements and mapping, in non-vacuum conditions, of low-Z elements down to Cl, S, and P that are of both environmental interest and technological importance. In this paper, an application of this novel synchrotron tool to elucidate the elemental distribution (microstructure) and chemical state (speciation) of Mn, Cl, S, and P-containing particulates emitted from automobile engines burning methylcyclopentadienyl manganese tricarbonyl- (MMT-) added fuel will be discussed in detail. Future opportunities of this microbeam technique in materials science and materials characterization will also be outlined.

Preparation and characterization of RF-PECVD deposited films containing β-C 3NN 4 microcrystallites

An attempt has been made to prepare crystalline β-C 3NN 4 using a PECVD (plasma enhanced chemical vapor deposition) process in which the nitrogen gas fraction was varied to determine the possible range for the formation of the crystalline β-C 3NN 4 phase. The cross-sectional morphology of the deposited films was observed using SEM (scanning electron miscoscopy). Chemical compositions and chemical states of elements in the deposited films were analyzed using XPS (X-ray photoelectron spectroscopy). XRD (X-ray diffraction) and (transmission electron microscopy) were used to characterize the film structure. Experimental results show that films containing β-C 3NN 4 microcrystallites can be prepared following the PECVD process. The coexistence of C-N and C=N bonding were confirmed. Nitrogen concentration of the deposited films increases with an increasing N 2 gas fraction; it depresses the formation of “disordered” and “graphitic” phase and favors the formation of C-N bonding, and as a result enhances the growth of β-C 3NN 4 microcrystallites. This work demonstrates that the carbon nitride films deposited by PECVD method may achieve the same results obtained by high-energy input processes.

Characterisation of archaeological bronzes using PIXE, PIGE, RBS and AES spectrometries

A reliable knowledge of the composition of archaeological bronzes for major and trace elements is of primary interest for the archaeologist. The composition of the metal artefacts gives information on the ancient technological knowledge and may help to distinguish between prehistoric cultural traditions. Pieces of bronzes from two pre-roman sites in Spain with different cultural traits have been analysed by ion beam analytical techniques (PIXE, PIGE and RBS) and Auger electron spectroscopy (AES). Joint use of these techniques has been found to be useful as they give complementary information on elemental composition and chemical state. The possible disturbance of the patina as a mask for the determination of the original underlying bronze composition has also been studied.

In-Situ X-ray Photoemission Spectromicroscopy of Electromigration in Patterned Al-Cu Lines With Maximum

AbstractWe report the application of a unique photoemission spectromicroscope (MAXIMUM) to the study of electromigration phenomena in Al-Cu interconnects. MAXIMUM is a scanning type photoemission microscope that uses multilayer-coated optics to focus 130 eV x-rays to a sub-0.1 µm spot. An electron energy analyzer collects photoelectrons in a chosen spectral region of interest to form an image of the sample that is sensitive to chemical states of elements on the sample surface. Al-Cu lines were characterized by spectromicroscopy techniques before and after electromigration stressing in the UHV environment of the microscope chamber. We present spectro-micrographs showing the chemical and structural changes on Al-Cu line surfaces as a result of the electromigration process.

Compositional changes of silicon carbide induced by nitrogen implantation

In order to form a composite of SiC and Si 3N 4 on a SiC surface polycrystalline SiC was irradiated with a 50-keV nitrogen ion beam with or without a hydrogen radical beam at elevated temperature up to 1100°C. The depth profiles, the chemical state of elements and the structure of the implanted surface were measured using RBS, NRA, AES, XPS and G-XRD. It was found that graphite-like carbon produced by the nitrogen implantation at 1100°C segregated at the surface and carbon depletion layer are formed beneath the surface. With increasing nitrogen fluence the replacement of carbon by nitrogen took place and β-Si 3N 4 crystallites were formed on the SiC surface. Preferential loss of carbon atoms in the implanted layer was promoted by irradiation with a hydrogen radical beam during the nitrogen implantation, and the amount of β-Si 3N 4 crystallites gradually increased.