Showing papers on "Chemical state published in 1987"
TL;DR: In this article, a deexcitation of metastable noble gas atoms (MDS) was used to follow the continuous oxidation of Cs films, which can be directly correlated with the associated change of the work function.
Abstract: Ultraviolet photoelectron spectroscopy (UPS) and electron spectroscopy by deexcitation of metastable noble gas atoms (MDS) were used to follow the continuous oxidation of Cs films. While UPS has a finite information depth, MDS probes only the properties of the outermost atomic layer. Small doses of O2 cause the formation of a ‘‘monolayer’’ of Cs11O3 in which the O2− ions are incorporated below the surface, while the surface itself consists merely of metallic Cs atoms. Further uptake of oxygen leads to a continuous transformation of the subsurface layer into Cs2O2, while a small concentration of adsorbed O atoms builds up on the surface which act as nucleation centers for subsurface oxidation. Finally, the surface layer is completely oxidized into CsO2 which then retards further oxygen penetration into the bulk. The chemical state of the surface can be directly correlated with the associated change of the work function. A monolayer of Cs adsorbed on a Cu(110) surface exhibits quite different properties.
128 citations
TL;DR: In this article, the effect of surface carbon on the catalytic activity of rhenium has been revealed for the first time, and the authors attributed the unique catalytic passivity of the graphite layer to its valence bond saturation.
77 citations
TL;DR: In this article, surface preparation techniques of aluminium for adhesive joining in aerospace applications and their influence on bond formation have been reviewed with attention to the effect of alloying elements and conditions of the technique.
Abstract: Surface preparation techniques of aluminium for adhesive joining in aerospace applications and their influence on bond formation have been reviewed. The mechanisms of the different pretreatments have been discussed with attention to the effect of alloying elements and conditions of the technique. On the basis of the morphology and physical and chemical state of the metal surface it has been attempted to characterize the adhesive-metal bond, its strength, and stability under adverse conditions.MST/546
47 citations
TL;DR: In this paper, the chemical properties of tritium formed in a LiF-BeF2 mixture were studied using a radiometric method and it was found that most of trite was found to be present in the T+ and T− states under no thermal treatment.
31 citations
TL;DR: In this paper, the diffusion properties of Group III and V elements in SiO2 are reviewed, including the differences due to different chemical states, ambient effects and concentration dependent diffusion.
25 citations
Journal Article•
15 citations
TL;DR: In this paper, the effect of covalency of Fe-O bonds on the magnetic properties of binary oxide glasses was discussed qualitatively, and it was explained based on the ionic character of chemical bonds between other cations and oxygen ions.
Abstract: Iron-containing binary oxide glasses in the systems of Fe 2 O 3 -P 2 O 5 , -TeO 2 , -SrO, -BaO, -PbO and -Bi 2 O 3 were prepared by using a twin-roller quenching method, and 57 Fe Mossbauer effect measurements were carried out on these glasses in order to determine the chemical state of iron ions. All the iron ions existed as Fe 3+ ions in all the glasses except Fe 2 O 3 -P 2 O 5 ones in which Fe 2+ ions coexisted. Fe 3+ ions in Fe 2 O 3 -P 2 O 5 and -TeO 2 glasses were laid on octahedral sites while they occupied tetrahedral sites in Fe 2 O 3 -SrO, -BaO, -PbO and -Bi 2 O 3 glasses. The covalency of Fe-O chemical bond was directly estimated from the isomer shift. The covalency was large in Fe 2 O 3 -SrO, -BaO, -PbO and Bi 2 O 3 glasses, while it was small in Fe 2 O 3 -P 2 O 5 and -TeO 2 glasses. This large dependence of the chemical state of iron ion on the kind of other cations coexisting with iron ions was explained based on the ionic character of chemical bonds between other cations and oxygen ions. Furthermore, the effect of covalency of Fe-O bonds on the magnetic properties of the glasses was discussed qualitatively.
15 citations
TL;DR: In this article, the effect of reducing gas mixture, H2-N2 or CO-N 2, on the cubic-hexagonal transition in BaTiO3 has been investigated by X-ray diffraction, ESR, ESCA, PAS and chemical analysis.
Abstract: The effect of reducing gas mixture, H2-N2 or CO-N2, on the cubic-hexagonal transition in BaTiO3 has been investigated by X-ray diffraction, ESR, ESCA, PAS and chemical analysis. The firing temperatures of BaTiO3 were 1380°C and 1500°C, and the transition temperature in air is already known to be 1460°C. The fractional conversion to the hexagonal phase increased with increasing concentrations of reducing gases, larger for samples fired in H2-N2 than those fired in CO-N2 for the same concentrations of the reducing gases. The hexagonal phase in all samples increased proportionally to the amount of Ti3+ produced by reduction of Ti4+ ions, regardless of the reducing gas species and firing temperatures. It was found that the minimum amount of Ti3+ ions to stabilize the hexagonal BaTiO3 at room temperature was 0.3% of total Ti ions. ESCA spectra due to Ti3+ were observed in the sample fired in 100% H2 at 1380°C.
14 citations
TL;DR: In this paper, the authors take the actual chemical environment explicitly into account in modelling the electron relaxation and the cascading de-excitation of a multiply ionized Si atom, as a representative example of a heavy-ion-bombarded target atom, and find that these post-collision processes have a universal non-discriminating nature provided that the valence electron supply of neighbouring atoms does not curtail the compensating interatomic valence charge transfer.
Abstract: By taking the actual chemical environment explicitly into account in modelling the electron relaxation and the cascading de-excitation of a multiply ionised Si atom, as a representative example of a heavy-ion-bombarded target atom, these post-collision processes are found to have a universal non-discriminating nature provided that the valence electron supply of neighbouring atoms does not curtail the compensating interatomic valence charge transfer. This finding is in obvious contradiction to the picture commonly presupposed in the literature, according to which the massive electron rearrangement occurring prior to X-ray emission fully accounts for the pronounced chemical effects on heavy-ion-induced X-ray satellite spectra. Thus one is led to reconsider a modification of the primary multiple-vacancy distribution through its projectile charge state dependence. The correlation of the effects with bulk chemical properties is now explained by the influence of the average valence electron density on the equilibrium charge state of energetic ions travelling in solids.
14 citations
TL;DR: In this paper, the interactions of monolayer Fe deposited on the Ni(100) surface with O 2 and C 6 H 5 NO 2 have been studied using X-ray photoelectron spectroscopy (XPS) and low energy electron diffraction (LEED).
13 citations
TL;DR: In this paper, the effects of anodization parameters, such as current density, electrolyte concentration, and anodisation time on the thickness and composition of the oxides formed on AISI 304L stainless steel anodized in H2SO4K2Cr2O7 were studied by low energy electron induced x-ray spectroscopy (LEEIXS), glow discharge optical spectroscopic (GDOS), and inert ion sputter profiling in conjunction with Auger electron spectrographs.
Abstract: The effects of anodization parameters, such as current density, electrolyte concentration, electrolyte temperature, and anodization time on the thickness and composition of the oxides formed on AISI 304L stainless steel anodized in H2SO4K2Cr2O7 were studied by low energy electron induced x-ray spectroscopy (LEEIXS), glow discharge optical spectroscopy (GDOS), and inert ion sputter profiling in conjunction with Auger electron spectroscopy. The physical and chemical properties of these films were correlated with the results of mechanical tests performed on adhesively bonded structures of the anodized pieces in order to test the feasibility of anodization as a prebond treatment for stainless steel.
Anodization in H2SO4K2Cr2O7 produces a Cr(III) enriched 100 nm thick oxide film. The novel technique of LEEIXS was used to characterize the chemical state of chromium while the hydrogen content of the anodic oxide was determined by GDOS.
TL;DR: The initial stage of oxidation of NiCr23 at room-temperature and oxygen pressures between 10−6 and 10−5 Pa has been studied by AES and XPS.
Abstract: The initial stage of oxidation of NiCr23 at room-temperature and oxygen pressures between 10−6 and 10−5 Pa has been studied by AES and XPS The composition of the surface during oxygen exposure was followed by continuously recording the Auger peaks of Ni (61 eV), Cr (529 eV) and O (510 eV) Photoelectron spectra from Ni 2p3/2, Cr 2p3/2 and O 1s were measured after different oxygen exposures to characterize the chemical state The thicknesses of the oxide layers were determined by angleresolved AES The elemental in-depth distribution was obtained by sputter depth profiling The results are explained by an initially preferential oxidation of Cr together with an oxygen-induced segregation of Cr, followed by enrichment and oxidation of Ni at the surface The thickness of the oxide after an exposure with 200 Langmuir oxygen was 13 nm, while for pure Ni it was only 063 nm
TL;DR: In this paper, a dilution method of correction for a strong self-absorption effect on the measurements of Kβ2/Kβ1,3 intensity ratios of arsenic, selenium and bromine is described.
Abstract: A dilution method of correction for a strong self-absorption effect on the measurements of Kβ2/Kβ1,3 intensity ratios of arsenic, selenium and bromine is described. The intrinsic intensity ratios obtained by the method are given and discussed for these elements in various states in powder and solution samples. The results are as follows: (1) the intensity ratio increases in the order As < Se < Br; (2) any element with a negative oxidation number gives a considerably larger intensity ratio than the same element with a positive or zero oxidation number; (3) the atoms surrounded by stronger electron donors give a larger intensity ratio; (4) a solution sample of a substance gives a larger intensity ratio than its powder sample, except for arsenic compounds; (5) a dilute solution sample below 0.1 M gives a larger intensity ratio than its concentrated solution sample, and its ratio is little affected by coexisting ions.
TL;DR: The application of static SIMS in characterising the chemistry of surfaces in basic and applied surface science is briefly demonstrated in this paper, where the ability of SSIMS to monitor the chemical structure and coverage of the adsorbed state is demonstrated with reference to CO and ethene adsorption on single crystal metals.
TL;DR: In this paper, the thermal release of oxygen from a high-Tc compound, YBa2Cu3O7, and subsequent changes of the chemical states were examined by a thermal desorption method and X-ray photoelectron spectroscopy.
Abstract: Thermal release of oxygen from a high-Tc compound, YBa2Cu3O7, and the subsequent changes of the chemical states were examined by a thermal desorption method and X-ray photoelectron spectroscopy. The former gives a spectrum with two peaks around 480°C and 700°C. The latter suggests that the 480°C peak corresponds to oxygens in the one dimensional CuO chains in the unit cell of the lattice, and the 700°C peak to one of the oxygens above and below the central copper atom. With the release of these oxygens, the copper atoms in the compound change from a pure Cu2+ state into a Cu1+ dominant state.
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TL;DR: In this article, the authors considered ionic bonds, covalent bonds, Lewis electron dot structures, polar molecules and hydrogen bonds, and bonding in solid-state elements, and considered the relationship between atoms and molecules.
Abstract: Overview of the chemical bond; considers ionic bonds, covalent bonds, Lewis electron dot structures, polar molecules and hydrogen bonds, and bonding in solid-state elements.
TL;DR: In this article, the chemical state and dispersion of the La and Co phases have been determined and the results were compared with the CO hydrogenation activity and selectivity of supported Co/alumina catalysts.
Abstract: Two series of La/alumina and CoLa/alumina catalysts have been characterized by several bulk and surface sensitive techniques. The chemical state and dispersion of the La and Co phases have been determined. The results were compared with the CO hydrogenation activity and selectivity of supported Co/alumina catalysts.
TL;DR: In this paper, the authors discuss the effects of different types of equipment on the performance of the system. But they do not discuss the impact of different kinds of equipment. And they focus on the effect of the hardware on the software.
Abstract: 生体試料の分析の分野においても,定性・定量分析だけでなく,含まれている元素の状態分析の必要性が高まっている.本研究では,ヒトの毛髪を試料に取り上げ,高分解能XRF法により試料に含まれる硫黄の状態分析が可能であることを示した.高分解能蛍光X線スペクトルは,二結晶型分光器{分光結晶:Ge(111)×2}を用いて測定した.更に得られた高分解能SKαスペクトルに対し,最小二乗法によるピーク分離法を適用して解析を行い,定量的な状態分析を行った.22種の標準物質の測定と,試料の測定及び解析から,ヒトの毛髪中の硫黄はS2-(有機物)が主成分であり(95～96%),S6+(無機物)がわずかに存在することが分かった.この二つの状態以外は存在しないことも分かった.中国人と日本人,男性と女性を対照させて検討した結果,硫黄の量,状態共に国籍の差が認められた.又,女性のほうがS6+がわずかながら多いことも認められた.一方黒髪と白髪を対比して検討したところ,白髪は黒髪に対しS2-が減少する傾向にあることが分かった.X線照射による損傷については.本研究での条件程度のX線(Cr,35kV,30mA)であれば,1時間強程度の照射ならば硫黄の状態が変化することはないことが明らかになった.
TL;DR: In this article, the electronic structure and chemical state of high-Tc superconductor (La1-xSrx)2CuO4-δ (x=0.075 and δ0.04) were studied by photoelectron spectroscopy.
Abstract: Electronic structure and chemical state of high-Tc superconductor (La1-xSrx)2CuO4-δ (x=0.075 and δ0.04) were studied by photoelectron spectroscopy. Resonant photoemission with synchrotron radiation snowed that the copper atom in the La–Sr–Cu–0 system is mostly divalent. The experimental results were compared with the band calculations performed for La2CuO4.
TL;DR: In this paper, the steady-state primary ion implantation volumes in Al, Si, Nb, Mo, Ta, and W could be analysed by scanning Auger microanalysis depth profiling, transmission electron microscopy, and electron diffraction imaging.
Abstract: Specimen modification in secondary ion microanalysis caused by oxygen primary ion bombardment has been studied for pure elements. The steady-state primary ion implantation volumes in Al, Si. Fe, Nb, Mo, Ta, and W could be analysed by scanning Auger microanalysis depth profiling, transmission electron microscopy, and electron diffraction imaging. The specimen region modified by the primary ions is found to consist of a metal–oxide phase mixture of various degrees of microcrystallinity, involving amorphous components, too. Whereas chemical state is represented by equilibrium compounds the lattice structure can be of metastable or quasi-equilibrium configuration.
TL;DR: The origin of the purple color of chromium-containing SnO2(Cr-SnO2) was studied mainly by ESCA, ESR and diffuse reflectance spectroscopies.
Abstract: Origin of the purple color of chromium-containing SnO2(Cr-SnO2) was studied mainly by ESCA, ESR and diffuse reflectance spectroscopies. It was found that when the Cr2O3 content in Cr-SnO2 was higher than 1.5wt%, the color of Cr-SnO2 is not purple but green due to the presence of Cr3+ in the aggregate state. ESCA and ESR analyses of the chemical state of chromium in Cr-SnO2 revealed that Cr6+, Cr5+ and Cr3+ are minor species when the Cr2O3 content in Cr-SnO2 was about 0.2wt%. Addition of Al3+ or Sb5+ to Cr-SnO2 gave rise to absorption bands at about 450 and 600nm or 470 and 650nm respectively, indicating that Cr5+ and Cr3+ in Cr-SnO2 are not responsible for the purple color (570nm). Consequently, the broad absorption band at 570nm was considered to be produced by Cr4+.
TL;DR: X-ray absorption near-edge structure (XANES) using synchrotron radiation excitation can be used to provide chemical speciation information for trace elements at concentrations as low as 10 ppm.
Abstract: Information concerning the chemical state of trace elements in biological systems generally has not been available. Such information for toxic elements and metals in metalloproteins could prove extremely valuable in the elucidation of their metabolism and other biological processes. The shielding of core electrons by binding electrons affect the energy required for creating inner-shell holes. Furthermore, the molecular binding and symmetry of the local environment of an atom affect the absorption spectrum in the neighborhood of the absorption edge. X-ray absorption near-edge structure (XANES) using synchrotron radiation excitation can be used to provide chemical speciation information for trace elements at concentrations as low as 10 ppm. The structure and position of the absorption curve in the region of an edge can yield vital data about the local structure and oxidation state of the trace element in question. Data are most easily interpreted by comparing the observed edge structure and position with those of model compounds of the element covering the entire range of possible oxidation states. Examples of such analyses will be reviewed.
TL;DR: In this article, the authors used nondestructive-depth profiling of non-Pd coated FeTi samples along with interfacial information from Pd-FeTi specimens to obtain unique insight into the decomposition process.
Abstract: FeTi is considered an excellent candidate for the reversible storage of hydrogen and has been studied extensively in an attempt to understand the bulk activation needed for this material before use. Segregation of TiO 2 to the surface has been noted to occur during activation explaining a slight loss of efficiency per hydride cycle, however, characterization by a host of bulk and surface sensitive techniques has not revealed the cause of this decomposition process. 10 nm FeTi samples were prepared in a UHV evaporator both with and without palladium coatings. Post treatment characterization was performed with backscatter c onversion e lectron M ossbauer s pectroscopy (CEMS), XPS and SIMS. CEMS is a powerful tool for providing stoichiometric, electronic, magnetic, chemical, and particle size information of iron at depths down to 100 nm. XPS and SIMS are useful to gain quantitative and chemical state information from the topmost 2 nm and the topmost monolayer, respectively. Activation treatments consisted of annealing at 573K and 623K followed by reduction at 573K. Results indicate that ppm levels of H 2 O in H 2 are sufficient to decompose the FeTi alloy and produce TiO 2 and Fe metal domains at the surface. Also, at 573K in vacuum, a solid-state reaction was found to occur between Fe oxides and FeTi to produce Fe metal and TiO 2 . The Pd-FeTi interface was probed with CEMS and the results demonstrate hydrogen dissociation and migration in the absence of alloy decomposition. Our approach uses nondestructive-depth profiling of non-Pd coated FeTi samples along with interfacial information from Pd-FeTi specimens to obtain unique insight into the decomposition process.
TL;DR: In this paper, X-ray photoemission spectroscopy (ESCA) and electron-induced Xray emission (EDAX) were used to analyze reactive sputtering on molybdenum surfaces.
Abstract: Zirconium containing coatings deposited by reactive sputtering on molybdenum surfaces were analysed by means of X-ray photoemission spectroscopy (ESCA) and electron-induced X-ray emission (EDAX), with an emphasis on zirconium carbide creation. For comparison ZrC layers deposited by cataphoresis were investigated. The results show that while EDAX is useful for bulk analysis of heavy atom contaminants, chemical state information vital for the reactive deposition processes is only obtained through ESCA. The spectra indicate that reactively sputtered zirconium leads to appreciable amounts of ZrC in the films only under special reaction conditions; if these are not present, unreacted Zr coatings are found, which transform to ZrO2 upon exposure to air. By monitoring the chemically shifted Zr 3d peaks the reaction conditions in the sputtering process which are favourable for ZrC deposition were determined.
TL;DR: In this paper, the ability of the Ni Lα, β, S Kβ, O Kα, and Ni 2p spectra to distinguish between chemical states of atoms and their various environments is applied for structural characterization of nickel coordination compounds.
Abstract: The ability of the Ni Lα, β, S Kβ, O Kα, and Ni 2p spectra to distinguish between chemical states of atoms and their various environments is applied for structural characterization of nickel coordination compounds. In addition to the well documented influences of metal oxidation state and the electronegativity, the dependence of the energy shifts and intensity ratios upon the coordination geometry and the chelate ligand structure is discussed.