Spectra of optical characteristics of titanium with a binary surface layer

The solution of the inverse problem of spectral ellipsometry is obtained for titanium with a surface layer of titanium oxide that was formed as a result of thermal (450°C) oxidation of the metal substrate. Using the Drude-Zener and Cauchy dispersion models, it is shown that a rather thick (46 nm) inhomogeneous binary surface layer including about 23% of titanium and 77% of titanium oxide is present on the studied samples of pure polycrystalline titanium. A natural weakly absorbing surface layer with a thickness of 13 nm is on this layer.     

Determination of Precious Metals in Geological Samples from Four Gold Ore Deposits of the North-East of Russia

Compositions of rare mineral phases containing precious metals (PMs) in samples from Natalka, Pavlik, Vetrenskoe, and Degdekan gold ore deposits (North-East of Russia) are studied by scintillation atomic emission spectrometry (SAES) and electron probe microanalysis (scanning electron microscopy and electron probe X-ray microanalysis, SEM–EPMA). The SAES method found dozens and hundreds of particles carrying gold, silver, and all platinum-group elements as native metals, intermetallides and solid solutions, arsenides, antimonites, sulfoarsenides, tellurides, selenides, etc. The variety of the elemental compositions of PM species (mineral phases) found by SAES significantly exceeds the list of minerals found previously by SEM–EPMA because of different natures of optical and X-ray spectra. The sizes of PM particles calculated by the SAES method and measured by SEM–EPMA are similar. The SAES data on the total concentrations of PMs satisfactorily agree with the results of inductively coupled plasma mass spectrometry.     

Calculation of the diffraction field in a layered medium illuminated through a phase mask

Optics and Spectroscopy - A local mode technique has been developed for calculating a diffraction field in a layered medium illuminated by the TE-polarized light through a phase mask with a...     

Catalytic Activity of Nickel Alloys in Anodic Oxidation of the Hypophosphite Ion as a Function of Their Composition

The rate of anodic oxidation of the hypophosphite ion on alloys Ni-P, Ni-B, and Ni-Mo-P is studied as a function of their composition and structure. The organic compounds that are customarily used to stabilize electrolytes of electroless nickel plating are shown to come useful when controlling composition of the Ni-P coatings at the expense of their different influence on the rates of partial processes of deposition of the alloy components. The formation of catalytic activity of such coatings is affected mostly by a structural factor. With alloys Ni-P, Ni-B, and Ni-Mo-P, whose composition was varied by altering the concentration of the source of the alloying component, dependence of catalytic activity of the surface on the composition is defined mainly by an electronic factor.__________Translated from Elektrokhimiya, Vol. 41, No. 8, 2005, pp. 972–980.Original Russian Text Copyright © 2005 by Sotskaya, Dolgikh, Ryabinina.     

Mode attenuation in microstructured optical fibers with absorbing coating

The characteristics of leaky modes in microstructured fibers with finite-thickness absorbing coatings are studied theoretically and experimentally. It is shown that, if the thickness of the coating is constant, the fiber has a quasi-periodic transmission spectrum. The period and depth of modulation of the spectrum are determined by resonance coupling between the modes of the fiber and coating. Since the constants of mode propagation in the coating are very sensitive to environmental parameters, the discovered effect seems to be promising for sensor applications.     

Waveguide spectroscopy of bilayer structures

A least-squares procedure is proposed for the reconstruction of optical parameters of bilayer structures. The objective function is constructed using experimental and calculated data on the reflectance of a coupling prism. A structure consisting of two different silicon oxynitride films on a silicon substrate is studied. The effect of scattering on the solution of the inverse problem is analyzed.     

The influence of electrolyte composition on pH of nickel hydrate formation

The influence of the composition of nickel plating electrolytes containing various ligands (Ac⁻, Gly⁻, and Asp²⁻) on pH of nickel hydrate formation (pH_hydr) was studied. The data obtained were interpreted from the point of view of ionic equilibria in the systems studied. The nature of sparingly soluble precipitates formed in these electrolytes when pH_hydr was reached was determined. Sparingly soluble precipitates were found to be pure Ni(OH)₂ hydroxides or basic salts with the composition Ni(OH) _n Cl_{2 − n} , in which the content of chloride ions increased as the concentration of NiCl₂ grew. Organic substance anions were absent in the precipitates formed and only influenced pH_hydr through changes in the concentration of free nickel ions as a result of complex formation. A principle of selecting the composition of nickel plating electrolytes was suggested on the basis of the results obtained.     

Anodic Oxidation of Hypophosphite on a Nickel–Phosphorus Electrode in the Presence of Some Organic Compounds

The effects some sulfur-, nitrogen-, or oxygen-containing organic compounds exert on the hypophosphite oxidation are compared. Catalytic and inhibiting effects of additives, which depend on their nature and occur in different concentration intervals, are discovered and examined. The inhibiting effect, exerted by all substances studied, is accompanied by a shift of steady-state potential in the positive direction and is determined by the adsorbability of substances, which is a function of the nature and number of heteroatoms and substituents. The best inhibiting properties are intrinsic to an additive with an –S–S– fragment and NH₂ groups. Catalytic influence, which is typical only for sulfur-containing compounds at low concentrations, is accompanied by a shift of steady-state potential in the negative direction and may be related to a surface modification and a change in the metal–hydrogen bond energy.