Local structure of core/shell nanocrystalline particles produced by surfactant-assisted ball milling of Fe powder in paraffin

Surfactant-assisted ball milling of the Fe powder in paraffin has been used for fabrication of core–shell nanocrystalline particles. The local atomic structure of the bulk and surface layers of the mechanically milled particles has been studied using X-ray absorption spectroscopic techniques with synchrotron radiation from the DORIS storage ring at DESY, Hamburg. Regardless of milling environment composition, the as-prepared powders were shown to be characterized by a significant drop in the EXAFS signal intensity and coordination numbers of the Fe–Fe pairs due to the formation of nanocrystalline state in the particles. It has been shown that an addition of perfluorononanoic acid as a surfactant has a more prominent effect on the structure of the shell layers. The effect is revealed as an appearance of light element atoms (O, F, C) in the local atomic environment of the Fe atoms due to formation of oxide, carbide and adsorbed structures of different types in the particle shell.     

Polyaniline films electrodeposited on iron from oxalic acid solution: spectroscopic analysis of chemical structure

Journal of Solid State Electrochemistry - Chemical structure of polyaniline electrodeposited on iron from oxalic acid solution has been studied by means of NEXAFS, Raman, and XPS spectroscopies....     

Molecular orientation in electrodeposited polypyrrole films

The molecular arrangement in electrodeposited polypyrrole films was studied by means of linear dichroism in the near-edge X-ray absorption fine structure (NEXAFS) spectra measured at the K absorption edges of carbon and nitrogen. It has been found that the change of the exciting radiation incidence from normal to grazing leads to an increase in the intensity of π*-related resonances with simultaneous decrease in the intensity of σ*-related resonances in the spectra. Similar changes in the spectra measured for both absorption edges indicate a pronounced conjugation of π-bonds in the polypyrrole chains in the grown films. Preferential in-plane orientation of pyrrole rings relative to the substrate surface is observed for all the deposited films. The linear dichroism is more pronounced at the initial stages of deposition (2D growth) than at later stages characterized by “cauliflower”-like morphology of the grown film.     

Study of Aluminum–Oxygen Binary Systems: Determination of Partial Interatomic Distances

This paper reports on an Auger-electron study of the oxidation of the perfect surface of polycrystalline Al in residual gas atmosphere at a partial pressure of oxygen of 10 ^-10 torr. Under supervacuum conditions, layer-by-layer oxidation of the aluminum surface takes place along with stabilization of the chemical composition of the oxide film. Oxygen can penetrate into the oxidation region not only by deposition from the residual atmosphere but also by other mechanisms. After the chemical composition of the oxide film was stabilized, its local atomic structure was studied by Al and O K-edge extended electron energy loss fine structure (EELFS) spectroscopy. The estimated partial interatomic distances for Al–Al, Al–O, O–Al, and O–O atomic pairs permitted us to conclude that an oxide-like phase is formed in the subsurface layers of aluminum oxidized under supervacuum conditions and to construct a model of the local atomic structure of this oxide-like phase.     

The electrochemical properties of Ni<Subscript>3</Subscript>C carbide

The electrochemical properties of Ni₃C was studied. In acidic sulfate solutions, the carbide is characterized by high overpotential of its oxidation as compared with nickel. In the case of carbide oxidation, the anodic reaction orders with respect to anions are low, indicating a weak dependence of the rate of the anodic process on the solution composition. Significant differences in the kinetics of the anodic processes indicate different mechanisms of the oxidation of nickel and its carbide. The rate and kinetic parameters of the hydrogen evolution reaction are comparable on Ni and Ni₃C. In neutral and alkaline solutions, the metal and carbide samples were similar in their electrochemical characteristics. The anodically grown oxide film is thinner on nickel carbide than on nickel metal, and the oxide formed on the carbide is more readily reduced under cathodic polarization. This film is also more resistant to the pitting attack than the oxide film on nickel metal.     

Formation of interfacial layer in Fe-polystyrene system during mechanochemical synthesis in the presence of alkyl surfactants

The structure of surface organic layers formed during the mechanical milling of Fe with polystyrene and alkyl surfactants is studied using NEXAFS and FT-IR spectroscopies. It is shown that the main constituents of the layers formed are condensed aromatic structures (products of the dehydrogenation of an organic medium) that contain covalently bound polystyrene fragments.     

Polyaniline films electrodeposited on iron from oxalic acid solution: linear dichroism of X-ray absorption and molecular arrangement

Journal of Solid State Electrochemistry - The linear dichroism in the near-edge X-ray absorption fine structure (NEXAFS) spectra measured at the K edges of carbon and nitrogen was used to analyze...     

Effect of sodium dodecyl sulfate and carbon particles/nanotubes on electrodeposition of polyaniline from oxalic acid solution

Journal of Solid State Electrochemistry - The effect of sodium dodecyl sulfate and carbon particles/nanotubes on the electropolymerization of aniline from oxalic acid solution onto a graphite...     

X-ray photoelectron study of the electronic structure of Fe systems

The possibility of magnetic property investigations and obtaining additional information is examined for compounds with various types of chemical bond, namely, FeX₂ (X = F, Cl, Br), Fe-Ge, Fe₅₀Co₅₀, and Fe₅₀Mn₅₀, using X-ray photoelectron spectroscopy. Translated fromZhurnal Struktumoi Khimii, Vol. 39, No. 6, pp. 1093–1097, November–December, 1998.