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 La_0.88Sr_0.12Ga_0.82Mg_0.18O_{3 –} 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.     

Calibration of sputtering yields for AES depth profiling of oxide layers on aluminium by means of carrier-gas heat extraction analysis

Summary For the purpose of obtaining suitable reference materials for technical coatings on aluminium, the feasibility of calibration of oxide layers by means of heat extraction was studied. Oxide layers were prepared on aluminium sheets by immersion in water of 50 or 80 ° C and annealing at 500 or 600 °C in argon atmosphere. The layer thickness was calculated from the oxygen content of the sample as measured by carrier-gas heat extraction analysis.The total sputtering yield of aluminium oxide layers was obtained via the correlation of AES depth profiling with heat extraction analysis results. This was demonstrated for high purity (99.9%) and technical purity (98.5%) aluminium with its original roughness from the rolling process, on which 20 to 1,000 nm thick oxide layers had been grown.The sputtering yields for the oxide layers prepared were found to be 3.9±0.8 atoms/ion, i.e., about four times higher than that for -Al₂O₃. Calibration of depth profiling on such technical quality oxide layers on aluminium was found to be feasible with a relative precision of 10 to 20%.

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Kalibrierung der Ionenzerstäubung zur AES-Tiefenprofilanalyse von Oxidschichten auf Aluminium durch Trägergas-Heißextraktion

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On leave from the Institute of Photographic Chemistry, Academia Sinica, Beijing, People's Republic of China     

Cyclic voltammetric behavior of Pd–Pt–Rh ternary alloys

The electrochemical behavior of Pd–Pt–Rh alloys has been investigated using cyclic voltammetry (CV). The alloys were prepared by electrochemical codeposition as limited volume electrodes (less than 1 m in thickness). The morphology of the alloy surface and bulk compositions were examined by the SEM/EDAX method. Surface oxides generation (oxygen adsorption) and oxides reduction (oxygen desorption) currents together with hydrogen adsorption and hydrogen absorption signals can be distinguished on CV curves. During potential cycling through the full hydrogen–oxygen potential range Rh and Pd are preferentially dissolved, which is reflected in a dramatic transformation in the voltammogram shape. The composition changes involve not only the surface but also some atomic layers beneath the surface.     

Electrolytic molybdenum oxides in lithium batteries

Nonstoichiometric molybdenum oxides (e-Mo_xO_y) were synthesized by cathodic reduction of aqueous ammonium and sodium molybdate solutions. Surface morphology of electrolytic (e) deposits, the chemical composition, crystal lattice structure, and the characteristics of electrochemical Li⁺ intercalation for such synthesized oxides were determined by the cation composition of molybdate solution and the conditions of deposit annealing. The electrochemical intercalation of Li⁺ ions in these Mo-oxides was investigated in thin-layer ballast-free electrodes, as a pasted mposite cathode in lithium batteries, and as an anode in lithium-ion batteries, with liquid organic and polymer electrolytes. The reversible discharge capacity of e-Mo₄O₁₁ synthesized from ammonium molybdate electrolyte in thin-layer ballast-free electrodes can exceed 225 mAh g^–1 for more than 170 cycles.     

Time-dependent emission of U from overheated UO2 pellets

The emission of uranium oxides from overheated nuclear fuels proceeds as a function of time, depending mainly on temperature, oxygen potential of the amosphere in contact, and structure and composition of the fuel matrix itself. This time dependent emission results in variation of the U-concentration in the released aerosol. The subsequent annealing (maturation) reactions acting on the aerosol particles are greatly affected by the emission sequence of the different elements. The maturation phase strongly influences the properties of particles dispersed in the environment: e.g. the rate of leaching of the particles is particularly sensitive to their chemical history.     

Analytical,structural and electrical characterization of SiGe layers by electron microbeam techniques

k-ratios of Ge-L and Si-K measured at different beam energies allow to evaluate simultaneously composition and thickness of SiGe layers on a Si substrate. A simple technique applying backscattered electrons also enables estimation of composition of bulk SiGe and of composition and thickness of relatively thick (200 nm) SiGe layers on Si. Electron channeling patterns of pseudomorphic SiGe/Si structures and of pure Si substrate show no significant differences whereas in relaxed structures a smearing of the pattern with increasing density of misfit dislocations is observed. Under particular conditions the technique of the electron beam induced current permits imaging of recombination-active misfit dislocations with a spatial resolution around 0.2 m. Moreover, a repulsion of holes due to the valence-band offset in a n-Si/SiGe heterostructure was detected.     

Thermodynamic analysis of the stability of titanium oxides in the TiO-TiO<Subscript>2</Subscript> range

The thermodynamic stabilities of titanium oxides in the composition range TiO-TiO₂, including Ti₂O₃, Ti₃O₅, and the homologous series Ti _n O_{2n ? 1} (n = 4–10), are compared by physicochemical simulation using the program package Selektor. The oxide composition is correlated with the states of titanium and oxygen in the oxide lattice. The phase transitions and chemical reactions in the oxides depend on the medium (air or water).     

X-ray microanalysis of thin film layered specimens containing light elements

Analysis of thin film layers on bulk substrates is carried out using a technique based on the (z) model of the depth distribution of X-ray emission. Both the composition and thickness of individual layers can be determined provided that the same element is not present in more than a single layer.The application of this method to the analysis of thin titanium-boron nitride bilayers on silicon or molybdenum substrates is discussed. X-ray intensities were measured by energy dispersive spectroscopy with a windowless or ultra thin window detector. The thickness of a 10 nm titanium layer could be estimated to within about ±1 nm, which is comparable with the depth resolution attainable by Auger sputter profiling.     

<Emphasis Type="Italic">In situ</Emphasis> XPS study of InAs oxidation in glow-discharge plasma

This is the first in situ XPS study of the InAs oxidation kinetics in glow-discharge plasma in the atmosphere of O₂ and CO₂ gases and in a mixture of O₂ and NF₃ gases. Chemical composition of the oxide films produced by cathodic and anodic polarization of samples was examined. Main regularities and features of the oxide film formation on the InAs surface in the normal and dark glow discharge modes were revealed. Normal glow discharge in oxygen-containing plasma was shown to form bilayer oxide films on the InAs surface. The bottom layer with thickness of some nanometers, which consists of arsenic and indium oxides, forms at the initial oxidation steps, its thickness remaining virtually unchanged. The upper layer consists of Al₂O₃ produced by sputtering of cathode material; it serves as a barrier to oxygen diffusion, its thickness building up linearly with the treatment time in glow-discharge plasma. Chemical composition of the growing proper InAs oxide film and the stoichiometry of subsurface region of a semiconductor substrate strongly depend on the oxidation process parameters. The obtained regularities are discussed.     

A DSC study of PVAC-PMMA two-stage emulsion polymers

Core-shell polymer colloids were produced by a two-stage emulsion polymerization technique. The polymers thus formed were investigated by means of differential scanning calorimetry (DSC). The DSC thermograms show two separate glass transition regions of the core and the shell component with positions unchanged regardless of chemical composition. Increases in specific heat capacity at the glass transition temperature of both components are lower than theoretical values calculated from the net chemical composition. From these results, it is possible to estimate i) the chemical composition of the interfacial layer and ii) the interfacial layer thickness. This interfacial layer thickness is in the order of 2–7 nm.Part 7 of Polymerizations in the Presence of Seeds     

Nanorods of Various Oxides and Hierarchically Structured Mesoporous Silica by Sol-Gel Electrophoresis

In this paper, we report the template-based growth of nanorods of oxides and hierarchically structured mesoporous silica, formed by means of a combination of sol-gel processing and electrophoretic deposition. Both single metal oxides (TiO₂) and complex oxides (Pb(Zr_0.52Ti_0.48)O₃) have been grown by this method. This method has also been applied to the growth of nanorods of mesoporous silica having an ordered pore structure, where the pores are aligned parallel to the long axis of the nanorod. Uniformly sized nanorods of about 125–200 nm in diameter and 10 m in length were grown over large areas with near unidirectional alignment. Appropriate sol preparation yielded the desired stoichiometric chemical composition and crystal structure of the oxide nanorods, with a heat treatment (500–700°C for 15–30 min) for crystallization, densification and any necessary pyrolysis.     

Nitrogen depth distribution, interface and structure analysis of SiNx layers produced by low-energy ion implantation

Thin silicon nitride (SiN _x ) layers with the stoichiometric N/Si ratio of 1.33 in the maximum of the concentration depth distributions of nitrogen were produced by implanting 10 keV¹⁵N ₂ ⁺ in 100 silicon at room temperature under high vacuum conditions. The depth distribution of the implanted isotope was measured by resonance nuclear reaction analysis (NRA), whereas the layer structure of the implanted region and the geometrical thickness of the layers were characterised by high resolution transmission electron microscopy (TEM). SiN _x layers with a thickness of about 30 nm were determined by NRA. Channeling Rutherford backscattering spectrometry was used to determine the disorder in the silicon substrate. Sharp interfaces of a few nanometers between the highly disordered implanted region and the crystalline structure of the substrate thickness were observed by TEM. The high thermal stability of SiN _x layers with N/Si ratios from under to over stoichiometric could be shown by electron beam rapid thermal annealing (1100 °C for 15 s, ramping up and down 5 °C/s) and NRA.     

Iron-Oxide–Titanium Anode for Electrolysis of Chloride Solutions

Electrophysical, electrochemical, and corrosion properties of iron-oxide-titanium anode (IOTA) in the electrolysis of chloride solutions are studied. An optimum thickness of the active mass of the IOTA coating (300 m) is substantiated. The anode lifetime during the production of sodium hypochlorite and electrotreatment of brackish water is defined by the corrosion wear of the coating active mass and is nine to ten thousand hours. Electrocatalytic properties of IOTA can be significantly improved by alloying the active mass of ferric–ferrous oxides with cobalt oxide during a plasma enhanced vapor codeposition of ferric–ferrous and cobalt oxides on a titanium support. An optimum ratio between ferric–ferrous and cobalt oxides in the active mass of the modified anode coating (IOTA-C) is determined. Electrocatalytic properties of IOTA-C in the sodium hypochloride production are identical to those of conventional DSA.     

Surface Properties of Nickel Electrodes in an Alkaline Electrolyte: An Ellipsometry Study

Adsorption of oxygen-containing species (OCS) on a polycrystalline nickel electrode in an alkaline electrolyte is studied by electrochemical and ellipsometric methods in the potential region from hydrogen evolution to oxygen evolution. It is concluded that OCS have stoichiometric composition Ni(OH)₂ up to 1.35 V. The potential of the OCS formation onset, the oxide monolayer thickness, and the surface coverage by OCS in the interval 0 1 are determined. The oxidation and reduction of a nickel oxide layer, repeatedly cycled at 1.35–1.5 V, suggests that this process is chemically reversible and the thickness of the oxide formed at 1.35 V is constant. It is shown that keeping the electrode under open-circuit conditions at 0.7–0.9 V for 10–20 h leads to the formation of nonelectroconducting oxide NiO _z .     

Reaction of dibenzylphosphine oxide with α,β-unsaturated O-methyloximes

The reaction of dibenzylphosphine oxide with O-methyloximes of some ,-unsaturated ketones results in the phosphorylation at the -carbon atom to form methoxyiminophosphine oxides, whereas the reaction of dibenzylphosphine oxide with O-methyloximes of ,-unsaturated aldehydes affords aminodihydrophosphole oxides.     

Synchrotron Microbeam Diffraction Study of the Microstructure and the Chemical Composition in a Monocrystalline Ni-Base Turbine Blade After a Thermomechanical Mission Test

High-performance turbine blades composed of monocrystalline Ni-base / superalloys are often protected by coatings to resist the high-temperature corrosive atmosphere environment applications. During applications severe thermal and mechanical loads cause drastic and complicated changes in the microstructure and the chemical composition, also combined with strong lateral gradients of both temperature and stress. Microbeam X-ray diffraction experiments with a spatial resolution of about 5 m enabled the determination of both the microstructural and the chemical composition gradients within material volumes of the sizes of the order of about 1 mm³ or smaller. The high angular and spatial resolution was achieved by a special focusing technique using a Bragg–Fresnel focusing monochromator at the BM5 beamline of the ESRF synchrotron at Grenoble. The X-ray diffraction experiments were complemented and supported by electron microscopy investigations of the microstructure and the chemical composition.     

Effect of in-situ γ-radiation on the sorption properties of hydrous oxides

Sorption of Li⁺, Cs⁺ and Sr²⁺ on hydrous titanium oxide and magnetite as a function of pH in the presence and absence of -rays has been studied. pH-titrations of the irradiated hydrous oxides have also been carried out. It has been shown that the sorption characteristics of these oxides are not altered by -irradiation and the uptake of metal ions is governed by the equilibrium pH of the solution. Certain physical changes observed on irradiating of the hydrous oxide samples in water are discussed.     

Growth, structure, and stability of ceria films on Si(111) and the application of CaF2 buffer layers

The growth of ceria (CeO2) films by oxidation of evaporated Ce metal on Si(111) and on CaF2(111) epilayers on Si(111) is compared. By use of XPS, UPS, and LEED, it has been demonstrated that the application of a CaF2 buffer layer between the ceria and Si substrate prevents the formation of an amorphous oxidized Si layer at the interface and permits the growth of a well-defined epitaxial ceria layer of (111) surface orientation. The thermal stability of the CeO2/CaF2/Si(111) interface structure is limited by the solid-state reaction between CaF2 and ceria. This leads to gradual migration of fluorine into the oxide at elevated temperatures to give a solid-state solution of fluorine in the partially reduced oxide. An analysis of the composition observed after extensive annealing in a vacuum suggests that, with initial layers of CaF2 and CeO2 of similar thickness, the ultimate product may be CeOF. The onset of this solid-state reaction can, however, be significantly delayed by annealing under an oxygen atmosphere.     

Comparative analysis of the composition, structure, and catalytic activity of the NiO-CuO-TiO2 on Titanium and NiO-CuO-Al2O3 on aluminum composites

The catalytically active oxide structures based on Al and Ti prepared by plasma-electrolytic oxidation (PEO) and additionally modified by impregnation with an aqueous solution of nickel and copper nitrates followed by annealing were studied. The oxide film-metal composites were studied using X-ray diffraction and X-ray spectroscopic analysis, X-ray electron spectroscopy, and electron microscopy. The catalytic activity of the composites in the reaction of CO oxidation was studied. In spite of differences in the elemental composition and morphology, the initial oxide layers on Al and Ti were comparable in terms of activity. Microgranules of size ～ 1 µm and formations from tens to hundreds of nanometers in size were detected on the surface of PEO layers. The modified layers contained crystalline CuO, NiO, and Al₂O₃ or TiO₂ phases. The surface layers of the modified structures about 3 nm in thickness on AMg5 aluminum alloy and VT1-0 titanium had the same elemental composition but exhibited different activity in the reaction of CO oxidation to CO₂.