True detection limit of rare earth elements in atomic emission analysis with an arc two-jet plasmatron

The “true detection limit” C_L,true was measured by a method proposed by Boumans et al. for 10 prominent lines of La, Ce, Pr, Nd and Sm, the most abundant rare earth elements (REEs) in geological samples. It is demonstrated how spectral interferences can increase of C_L,true. The spectra were excited in an argon arc plasma jet with evaporation powders of five complex natural samples. The data show that there is a significant increase of C_L,true in real samples containing large concentrations of such elements as Ti, Zr, Cr, Nb, Ta and REEs emitting complex spectra. Received: 17 June 1997 / Revised: 20 October 1997 / Accepted: 26 October 1997     

Calibration model of simultaneous multielement atomic-emission analysis using analytical line groups of each determined element

A calibration model of multielement methods for simultaneous determination of micro- and macro-concentrations of elements by computing the arc atomic-emission spectra has been developed. A calibration procedure for the analytical line group of the elements to be determined is offered. It allows the lower and upper limits of the concentration range for each line of the determined element to be calculated by means of the least-square method (LSM) and the Weibull distribution law is used to extend the concentration region. The calibration model was successfully tested for different arc optical emission spectroscopy (OES) methods. Received: 17 June 1997 / Revised: 3 November 1997 / Accepted: 7 November 1997     

Behavior of a ruthenium-titanium oxide film electrode (RTOE) in potentiometry

Polyfunctional properties of a ruthenium-titanium oxide electrode in the absence of polarization and the possibility of its application to the potentiometric detection of iron(III) titration with an ethylenediaminetetraacetic acid solution, acid-base and redox reaction types have been demonstrated. Mechanisms of reactions determining the potentials of electrodes of this type have been investigated by a number of methods.     

Isotherm of α-tocopherol adsorption on acid-activated clinoptilolite tuff

Adsorption of α-tocopherol from ethanol solution on clinoptilolite tuff activated with 4.0 M HCl is studied. α-Tocopherol adsorption isotherm is analyzed using the Langmuir, Freundlich, and Redlich-Peterson adsorption theories. The adsorption of α-tocopherol from dilute solutions on this sorbent is ascertained to be described by the Langmuir model.     

An effect of heat processing on catalytic activity of a system MnO x ,SiO2/TiO2/Ti

An effect of annealing in air at temperatures 250, 350, 500, and 700°C on composition, surface structure, and catalytic activity in CO oxidation of a system MnO _x ,SiO₂/TiO₂/Ti formed by combining methods of plasma electrolytic oxidation and impregnation was examined.     

Plasma-electrolytic formation, composition and catalytic activity of manganese oxide containing structures on titanium

In the present work, we report the data about formation of TiO₂-rutile or TiO₂ and Mn₂O₃, Mn₃O₄ containing oxide structures on titanium in aqueous electrolytes by means of plasma-electrolytic deposition. The layers formed are characterized by X-ray diffraction, electron probe microanalysis and scanning electron microscopy methods. The PEO coatings on titanium formed in sodium tetraborate solution contain the TiO₂ stabile rutile modification that is important when utilizing such a structure as a catalyst carrier. Manganese acetate adding into the electrolyte leads to formation of layers that contain Mn₂O₃, Mn₃O₄ and TiO₂-rutile in outer region. The manganese content in the surface layer depends on the formation conditions as well as on manganese acetate concentration in the electrolyte. Catalytic activity of the layers in CO → CO₂ reaction is studied in the static and flow conditions. The manganese-containing layers obtained possess the catalytic activity in CO → CO₂ oxidation reaction at the temperature range of 250-350 °C. The catalytic activity depends on the concentration and surface distribution of manganese as well as on the layers morphology.     

Effects of evaporation and melting on nonstoichiometry and inhomogeneity of LiInSe<Subscript>2</Subscript> crystals

Evaporation and compositional changes of the liquids above the melting point of LiInSe₂ crystals have been characterized quantitatively by using special techniques of a rapid thermal analysis and differential dissolution. The occurrence of a liquid immiscible region in the Li₂Se-rich side of the Li₂Se-In₂Se₃ diagram and incongruent evaporation with the preferential evaporation of In₂Se₃ rising markedly above boiling point were determined from the peaks on the thermal curves and from precise control over the composition of the vapour and residual solid as a function of temperature. It was shown that both the processes could be the sources of nonstoichiometry and inhomogeneity of the LiInSe₂ crystals.     

One-Pot Synthesis of N-2,4-Enyne Cyclic Amines

Russian Journal of General Chemistry - Stereoselective synthesis of N-2,4-enyne cyclic amines was performed by one-pot animation of individual isomers of 1,3-dichloropropene and the subsequent...     

Thermal air-oxidized coating on Yb14−xRExMnSb11 ceramics

Journal of Thermal Analysis and Calorimetry - A high sublimation rate of Yb14MnSb11 as a promising thermoelectric material at working temperatures is a critical factor for its space power...     

Plasma electrolytic synthesis and characterization of pH-sensitive TiO2-ZrO2-ZrTiO4-CeOx films on titanium

Journal of Solid State Electrochemistry - The Ti/TiO2 + ZrO2, Ti/TiO2 + CeOx, and Ti/TiO2 + CeOx + ZrO2 composites, including Y-doped ones, have been...