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...     

Metallocene-containing conjugated polymers

The paper gives a review of publications on polymers with conjugated matrices (PPy, PTh, PAni, hydrocarbon or mixed chains...) which incorporate metallocene complexes (Fe, Ru, Co; Ni, Ti, Zr, Ta) with two cyclopentadienyl ligands (Cp) and their derivatives, in particular with methylated cyclopentadienyl rings (Cp*), as well as hemi-metallocene complexes (Fe, Ru, Co, Mn), as pendant groups or inside the principal chain (part B). The information on related short-chain systems, monomers and oligomers, is also included. In part A, a brief overview of various conjugated polymer materials is presented, with their classification in accordance with the conductivity mechanism (ionic, electronic or mixed conductors) or with the structural type (linear-chain organic or mixed polymers, derivatization, metallopolymers, multi-dimensional structures, alternating and block copolymers with organic or mixed units, hybrid materials with a mixture of conjugated and inert polymers, polymers inside a solid matrix, conjugated polymers with incorporated nanoelements of transition metals, carbon, semiconductors etc.     

Formation of RNA oligonucleotides over the mineral surface preliminary irradiated with UV light

An opportunity of the abiogenic formation of oligonucleotides over the surface of montmorillonite particles, preliminarily irradiated with UV light, was found upon the adsorption of mononucleotides on this surface. A probable mechanism of such a synthesis is suggested.     

Modification of Arabinogalactan Isolated from Larix sibirica Ledeb. into Sulfated Derivatives with the Controlled Molecular Weights

The process of sulfation of arabinogalactan—a natural polysaccharide from Larix sibirica Ledeb.—with sulfamic acid in 1,4-dioxane using different activators has been studied for the first time. The dynamics of the molecular weight of sulfated arabinogalactan upon variation in the temperature and time of sulfation of arabinogalactan with sulfamic acid in 1,4-dioxane has been investigated. It has been found that, as the sulfation time increases from 10 to 90 min, the molecular weights of the reaction products grow due to the introduction of sulfate groups without significant destruction of the initial polymer and sulfation products. Sulfation at 95 °C for 20 min yields the products with a higher molecular weight than in the case of sulfation at 85 °C, which is related to an increase in the sulfation rate; however, during the further process occurring under these conditions, sulfation is accompanied by the destruction and the molecular weight of the sulfated polymer decreases. The numerical optimization of arabinogalactan sulfation process has been performed. It has been shown that the optimal parameters for obtaining a product with a high sulfur content are a sulfamic acid amount of 20 mmol per 1 g of arabinogalactan, a process temperature of 85 °C, and a process time of 2.5 h.     

Characteristics of Interactions in the Pectin–Chitosan System

Interpolymeric complexes have been obtained from citric pectin and chitosan, the latter synthesized from crab chitin. The composition and structure of complexes obtained from different ratios of the components were studied by IR spectroscopy, rheological investigation of gel structure, and mathematical modelling of system properties. Rheological investigation of the processes involved in the formation of interpolymeric complexes with gel structures from citric pectin and chitosan was conducted in moderately concentrated solutions containing different ratios of the components. It was shown that the toughness of the gel structures was determined by the ratio of the amounts of the heterogeneous polymers. The toughest product (τ=121.4 Pa) was obtained by use of equimolar quantities of pectin and chitosan. With deviation of the composition of the mixture from equimolar the toughness of the gel decreased. It is proposed that the polyelectrolyte pectin–chitosan complex with a network structure is formed at the expense of electrostatic interaction between positively charged amino groups at C-2 of the chitosan pyranose ring and negatively charged carboxyl groups at the C-5 of the pectin pyranose ring.     

Study of MgO/MgAc2 catalyst activity inn-butane pyrolysis

Distributions ofn-butane pyrolysis products and activities of catalysts have been analyzed. The catalysts based on magnesium oxide was preparedvia modification with magnesium acetate.n-Butane decomposition is shown to be accelerated due to active surface centers of at least two types.     

Extractive concentration of platinum-group elements and their determination by atomic-absorption spectrophotometry

The extraction of Pt, Pd, Ir, Rh, Ru, Ag, Au, Co, Cu, Ni and Fe with n-octylaniline has been investigated. Noble metals are extracted 10(3)-10(4) times better than Cu, Ni, Co and Fe. A method of determination of Pt, Pd, Ir, Rh and Ru is proposed. They are first separated from Cu, Ni, Co and Fe by means of extraction (and then determined, in either the aqueous or organic phase, by atomic-absorption spectrophotometry. The atomic absorption of platinum metals (with the exception of Pd) is affected by other elements of the platinum group and by non-noble metals. La(NO(3))(3) and Nd(NO(3))(3) lower the limit of detection for Pt, Rh, Ir and Ru and inhibit the effect of Co, Cu, Ni, Fe, Bi, Zn, Na, etc. on their determination. Lanthanum and neodymium chlorides and sulphates produce a similar effect but only on the determination of Pt and Rh. The coefficient of variation of the determination, in both phases, is within 2-6.8%.     

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     

Phase equilibrium and intermediate phases in the Eu–Sb system

Rapid heating rate thermal analysis, X-ray diffraction, fluorescence spectrometry, and differential dissolution method were used to study the high-temperature phase equilibrium in the Eu–Sb system within the composition range between 37 and 96 at% Sb. The techniques were effective in determination of the vapor–solid–liquid equilibrium since intermediate phases except Eu₄Sb₃ evaporated incongruently after melting. A thermal procedure was developed to determine the liquidus and solidus lines of the T−x diagram. Six stable phases were identified: two phases, EuSb₂ and Eu₄Sb₃, melt congruently at 1045±10 °C and 1600±15 °C, the Eu₂Sb₃, Eu₁₁Sb₁₀, Eu₅Sb₄, and Eu₅Sb₃ phases melt incongruently at 850±8 °C, 950±10 °C, 1350±15 °C, and 1445±15 °C, respectively. The exact composition shifting of Sb-rich decomposable phases towards Eu₄Sb₃, the most refractory compound, was determined. The topology of the Eu–Sb phase diagram was considered together with that of the Yb–Sb system.     

Thermodynamic investigation of the systems <Emphasis Type="Italic">Ln</Emphasis>Se<Subscript>2</Subscript>–<Emphasis Type="Italic">Ln</Emphasis>Se<Subscript>1.5</Subscript> (<Emphasis Type="Italic">Ln</Emphasis> = La,Nd)

A detailed thermodynamic study of the systems LnSe₂–LnSe_1.5 (Ln = La, Nd) was performed by static method of vapour pressure measurement using quartz membrane-gauge manometers within the temperature range 713–1,395 K. The p _Se–T–x dependences obtained in this study have shown that the phase regions in composition intervals studied consist of discrete phases: LnSe_1.95 LnSe_1.90, LnSe_1.85, LnSe_1.80 (Ln = La, Nd). The enthalpies and the entropies for the stepwise dissociation process were calculated from the experimental data. The standard enthalpies of formation and the absolute entropies were estimated for the compounds investigated using literature data.