Search results for " Spectroscopy"
showing 10 items of 6851 documents
Effect of the surface stoichiometry on the interaction of Mo with TiO2 (110)
2000
Abstract Molydenum has been deposited at room temperature on (110) TiO2 surfaces with different stoichiometries, roughnesses and crystallinities. Whatever the substrate preparation is, in-situ Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS) studies as well as ex-situ atomic force microscopy (AFM) and reflexion high-energy electron diffraction (RHEED) studies reveal a Stranski–Krastanov growth mode: the completion of three monolayers followed by islands growth is observed in every case. The three monolayers are always composed of amorphous molybdenum oxide with an oxidation state of molybdenum less than IV. The oxidation of the molybdenum layers generates Ti3+ an…
Initial chemical transport of reducing elements and chemical reactions in oxide cathode base metal
2002
Abstract In the present work, the formation of compounds associated to the diffusion of reducing elements (Mg and Al) to the nickel surface of a one-piece oxide cathode has been studied. Those compounds have been evidenced after the annealing steps at high temperature performed on cathode base metal prior to the emitting coating deposition. Therefore, they form the “initial” interface between the nickel and the coating, in other words, the interface existing at the beginning of cathode life. Extensive analysis to characterize the nickel base prior to coating deposition has been performed by means of scanning electron microscopy (SEM) coupled with energy dispersive X-ray spectroscopy (EDX), …
Diamond nucleation on iridium: local variations of structure and density within the BEN layer
2009
Abstract The diamond nuclei generated by the bias enhanced nucleation (BEN) on iridium are gathered in well defined areas (“domains”). In atomic force microscopy (AFM) measurements they become manifest in a 1 nm downward step. The fine structure of the carbon layer inside and outside these domains has been studied by small spot Auger electron spectroscopy (AES), high resolution transmission electron microscopy (HRTEM), AFM and lateral force microscopy (LFM). The Auger spectra of the carbon KLL peak taken in an ultra high vacuum setup revealed diamond features inside and more graphitic features outside the domains. The comparison with the intensity of the Auger signal originating from the un…
Influence of the passive film properties and residual stresses on the micro-electrochemical behavior of duplex stainless steels
2010
In the present paper, the chemical composition of passive films formed on both phases of two types of duplex stainless steels (UNS S31803 and UNS S32304) is determined at the micro-scale using Auger electron spectroscopy (AES). Samples were either mechanically polished (down to diamond pastes) or electrochemically etched in acidic solutions. The micro-electrochemical behavior of samples was then determined in sodium chloride media by means of the electrochemical micro-cell technique (capillary diameters of 30 μm). The results obtained were analyzed considering the passive film chemical composition. Quantitative relationships between electrochemical parameters and the distribution of chromiu…
Passive properties of lean duplex stainless steels after long-term ageing in air studied using EBSD, AES, XPS and local electrochemical impedance spe…
2013
Abstract Passivity of duplex stainless steel was studied after long-term ageing in air using local electrochemical impedance spectroscopy, AES, XPS and EBSD. After mechanical polishing, the passive film was homogeneous and had a capacitive behaviour described by the CPE. After long-term ageing, a small thickening was detected and O2−/OH− was significantly higher in the austenite than in the ferrite. Austenite behaved as a blocking electrode whereas two capacitive loops were observed in the ferrite (low value of O2−/OH). The loop at high frequencies was related with the oxygen reduction and the loop at low frequencies was connected with the passive film.
Relationships between the Impedance of Oxide Scales on Martensitic and Austenitic Steels and Corrosion Rate in Liquid Lead-Bismuth Eutectic
2004
Abstract The impedance properties (resistance and capacitance) of oxide scales on the martensitic/ferritic steel HT-9 and austenitic stainless steel Type 316L (UNS S31603) were examined during immersion in lead-bismuth eutectic (LBE) using a technique similar to electrochemical impedance spectroscopy. These scales were created by preoxidizing the samples in an air/water vapor environment at 800°C for various times prior to immersion in LBE. Calculation of oxide conductivity for samples immersed in LBE at 200°C for 200 h yielded σHT9 ≈ 4 × 10−7 (Ω × cm)−1 while σ316 ≈ 3 × 10−8 (Ω × cm)−1. The influence of temperature alone gave the anticipated Arrhenius behavior with Ea equal to 0.12 eV, whi…
A corrosion study of austenitic and martensitic steels under boiler conditions by means of 57Fe conversion electron mössbauer spectroscopy
1978
Abstract The growth of protective oxide layers on a martensitic FeCr (1.4122) and two austenitic FeCrNi steel samples (1.4550 and Incoloy 800) was studied by means of the 57Fe Conversion Electron Mossbauer Spectroscopy (CEMS). Scanning electron microscopy was applied to characterize the topographical nature of the oxide layers. Following a technical procedure of running-in steam generators, the steel specimens were oxidized in oxygen-free water at 295°C, 142 bar and a pH value between 9 and 10 for periods up to 70 h. In the case of the steels 1.4122 and 1.4550 the only oxide phase detected was non-stoichiometric magnetite, whereas nickel ferrite of nonstoichiometric composition was found…
ODS steel raw material local structure analysis using X-ray absorption spectroscopy
2015
Oxide dispersion strengthened (ODS) steels are promising materials for fusion power reactors, concentrated solar power plants, jet engines, chemical reactors as well as for hydrogen production from thermolysis of water. In this study we used X-ray absorption spectroscopy at the Fe and Cr K-edges as a tool to get insight into the local structure of ferritic and austenitic ODS steels around Fe and Cr atoms and its transformation during mechanical alloying process. Using the analysis of X-ray absorption near edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) we found that for austenitic samples a transformation of ferritic steel to austenitic steel is detectable after …
A Ferromagnetic [Cu3(OH)2]4+Cluster Formed inside a Tritopic Nonaazapyridinophane: Crystal Structure and Solution Studies
2009
The characterization of molecular alkaly metal azides
2006
Matrix isolation infrared (IR) studies have been carried out on the vaporisation of the alkali-metal azides MN(3) (M = Na, K, Rb and Cs). The results show that under high vacuum conditions, molecular KN(3), RbN(3) and CsN(3) are present as stable high-temperature vapour species, together with variable amounts of nitrogen gas and the corresponding metal atoms. The characterisation of these molecular azides is supported by ab initio molecular orbital calculations and density functional theory (DFT) calculations, and for CsN(3) in particular, by the detection of the isotopomers CS((14)N(15)N(14)N) and Cs((15)N(14)N(14)N). The IR spectra are assigned to a "side-on" (C(2v)) structure by comparis…