Showing papers in "Russian Journal of Applied Chemistry in 1997"

Carbonization of polymers

Abstract: Publications concerning carbonization of polymers are reviewed. It is shown that thermochemical transformations of polymers into carbon structures are closely related to natural metamorphism of plant raw material in natural coals. The role of heteroatoms in carbonization of polymers is emphasized. The main criteria for estimating the degree of carbonization are proposed.

Formation of quinone methides : An alternative pathway of thermal degradation of some β-O-4-ethers as compounds modeling lignin

Abstract: Energy of the homolytic cleavage of the β-O-4 bond in quinone methide formed by dehydration of 1-4-hydroxy-3-methoxyphenyl)-2-(2-methoxyphenyl)-]-propanol is calculated. The data obtained explain a low thermal stability of lignin-modeling compounds containing a benzyl alcohol group and a free phenolic hydroxyl.

Synthesis of D(+)-glucosamine hydrochloride

Abstract: Acid hydrolysis of chitin, separation and purification of D(+)-glucosamine hydrochloride from hydrolyzate, and the composition and quality of the resulting product are studied. A new route to D(+)-glucosamine hydrochloride is proposed, eliminating the stage of hydrolyzate clarification with activated carbon and simplifying certain other operations.

Rate of electrochemical aluminum anodizing and volume growth of anode oxide in orthophosphoric acid solutions

Abstract: The influence is studied of the anodic current density and orthophosphoric acid concentration in the electrolyte on the rate of electrochemical anodizing of aluminum and on the volume growth of the anodic oxide.

Liquid-vapor, liquid-liquid, and liquid-liquid-vapor phase equilibria in water-acetic acid-propyl acetate system at 313.15 K

Abstract: Results of the experimental study of phase equilibria are given for water-acetic acid-propyl acetate ternary system under isothermal conditions (313.15 K).

New lines in lead battery scrap recycling

Abstract: The scope of problems concerning improvement of recycling methods for lead battery scrap, the most important and complex kind of secondary lead raw materials, is examined. An important role of desulfation of active mass, allowing utilization of sulfur and, therefore, its elimination from the reduction process, is emphasized. Some new processes for lead recovery from secondary raw materials are considered.

Ceramic coatings for carbon materials

Abstract: Multicomponent ceramic coatings containing oxides and oxygen-free high-melting compounds were synthesized on the surface of carbon materials.

High-temperature electrochemical synthesis of zirconium diboride powders from chloride-fluoride melts

Abstract: Zirconium diboride powders were obtained by electrolysis of a molten KCI-KF eutectic mixture, containing 15 wt % K 2 ZrF 6 and 15 wt% KBF 4 , in the range of cathode current density from 0.3 to 1.0 A cm -2 at 1023 K. The effect of cathode current density on the average size of zirconium diboride crystals was studied.

Production of magnesium hydroxide from residual natural brine when extracting salt from seawater

Abstract: To obtain Mg(OH) 2 from natural brine remaining in salt production from seawater at ordinary temperature, a two-stage procedure was put forward: the desulfation of the residual natural brine on reaction with crystalline CaCl 2 or its solutions with various concentrations and the precipitation of Mg(OH) 2 using lime milk or dolomite milk. A broad-scale experiment was performed to confirm the results of laboratory test. A closed-circuit processing scheme was proposed.

Effect of synthetic conditions on structural characteristics of hydroxylapatite

Abstract: Hydroxylapatite Ca 5 (PO 4 ) 3 OH with varied degree of crystallization and contents of CO 3 2- ions in the structure, as estimated by X-ray phase analysis and IR spectroscopy, was obtained by three synthetic procedures. The effect of crystallization conditions (concentrations of starting reagents, pH, and temperature of product crystallization) on the structural characteristics of resulting hydroxylapatite was studied. The efficiency of these synthetic procedures was estimated in terms of product yield, product quality, and energy consumption.

Structural modification of manganese(III, IV) oxides in synthesis of sorbents selective to strontium

Abstract: Sorbents selective to strontium ions and radionuclides were synthesized by thermal modification of manganese(III, IV) oxides with birnessite structure containing Sr 2+ ions. The sequence of phase transitions in the birnessite-psilomelane-cryptomelane-strontium permanganite system was determined hy thermal and X-ray diffraction analyses. The psilomelane phase was selected as a basis for obtaining sorbents since it provided the best sorption properties of the resulting materials. The temperature conditions of the synthesis were substantated.

Liquid-vapor equilibrium in the acetic acid-n-propyl alcohol-water system at 313.15 K

Abstract: Liquid-vapor equilibrium in the acetic acid-n-propyl alcohol-water ternary system and acetic acid-n-propyl alcohol binary subsystem was studied experimentally under isothermal conditions (313.15 K).

Electrochemical deposition of PbSe, PbTe, and PbSe1-xTex films

Abstract: Cathodic electrodeposition of PbSe 1-x Te x films from acidic aqueous solutions containing Se(IV), Te(IV) in the anionic form and Pb(II) cations was studied. The composition of the solid solutions electrodeposited at various Se(IV) and Te(IV) concentrations was determined using the lattice cell parameters found by X-ray analysis.

Electrochemical deposition, structure, and properties of nickel-diamond coatings

Abstract: Specific features of the electrodeposition process, phase composition, structure, physicomechanical (microhardness, wear rate), and corrosion-electrochemical properties of composite nickel-based electroplated coatings incorporating diamond macroparticles were studied. The influence of electrolysis regimes and granulometric composition of diamond powder on the phase composition and properties of coatings was analyzed. Conditions are optimized for preparing nickel-diamond coatings with enhanced resistance to wear and corrosion.

Hydrolytic polycondensation of tetraethoxysilane with metal salts and oxides in sol-gel process

Abstract: Hydrolysis of tetraethoxysilane catalyzed by ammonium hydroxide was studied as influenced by the reagent ratio and solvent nature. Polycondensation of tetraethoxysilane with Group I, II, and IV metal salts and oxides in 2-propanol was studied in the presence of NH 4 OH.

Heme-containing hydroperoxide test systems for inhibitors of free-radical reactions

Abstract: Rates of initiation of active oxygen-containing radicals in test systems consisting of hemin (methemalbumin) and tert-butyl hydroperoxide or H 2 O 2 are estimated using o-phenylenediamine and 3,3',5,5'-tetramethylbenzidine as acceptors of free radicals. The criterion of inhibitor efficiency is the ratio k Cat /K m (1 mot -1 s -1 ), determined from the Michaelis-Menten dependences for growing concentrations of inhibitors being oxidized.

High-swelling polymer hydrogels : Certain present-day problems and prospects

Abstract: Present-day fundamental problems of the physical chemistry of high-swelling (mainly charged) polymer networks are examined. In analyzing different approaches to description of the behavior of hydrogels under various conditions, attention is focused on unclear or unresolved problems. Also considered are the least understood aspects of practical application of high-swelling hydrogels to purification and ore-concentration, biotechnology, and fabrication electro- and chemomechanical transducers and optical elements, and also the prospects of using hydrogels in high technologies.

Iron oxide block catalyst for catalytic burning of fuels

Abstract: The state of iron in iron oxide catalysts prepared by impregnating multichannel block ceramic supports with solutions containing iron (III) oxalate complexes in various concentrations is studied by X-ray phase analysis, temperature-programmed reduction, electronic diffuse reflection spectroscopy, and adsorption and chemical phase analyses.

Photooxidative purification of water to remove organochlorine pesticide 2,4-D (2,4-dichlorophenoxyacetic acid)

Abstract: Photooxidative destruction of aqueous solutions of an organochlorine pesticide, 2,4-D (2,4-dichlorophenoxyacetic acid) was studied for the cases of UV irradiation with and without simultaneous treatment with hydrogen peroxide. The method is shown to be promising for use in engineering practice to remove organochlorine pesticides from water.

Electrochemical behavior of nonstoichiometric copper sulfide in nickel and copper plating solutions

Abstract: The electrochemical behavior of nonstoichiometric copper sulfide Cu 2-x S coatings was studied by potentiodynamic voltammetry in nickel plating and sulfuric and cyanide copper plating electrolytes. Conditions of electrodeposition of metals on an electrically conducting Cu 2-x S layer are determined.

Effect of maleic acid imides on rheological properties and radiation-induced three-dimensional polymerization of solid epoxy acrylate oligomer

Abstract: Effect of maleic acid imides on rheological properties and radiation-induced three-dimensional polymerization of solid epoxy acrylate oligomer is studied.

On the problem of extraction of organic solvents from saturated absorbent

Abstract: A process is described of extracting organic solvents from a high-boiling organic absorbent after their absorption from air flow.

Waste-free process for production of castable polyurethanes

Abstract: Two methods are developed for thermochemical degradation of castable polyurethanes to recover raw materials and improve the ecological situation. Degradation products are analyzed by IR spectroscopy, and degradation mechanisms are proposed. Castable polyurethanes are prepared from polyesters containing degradation products.

Peculiarities of the mechanism of electrochromic coloring of oxide films upon pulsed electrochemical polarization

Abstract: Electrochromism in transition metal oxides on polarization with pulses of low on-off time ratio is discussed.

Fundamental aspects of deposition of copper compounds in supercritical pressure power unit turbine

Abstract: Processes of formation, transfer, and deposition of copper corrosion products (CuO, CU 2 O) in the water-steam circuit of supercritical pressure power units are substantiated qualitatively and quantitatively by simulation and solubility calculations. Measures intended to reduce the amount of deposits and increase the turbine power in various water-chemical regimes of the circuit are discussed.

Titanium(IV) hydrolysis in ammonium sulfate solutions in production of mica-based nacreous pigments

Abstract: On the basis of studying titanium(IV) hydrolysis in ammonium sulfate solutions in the presence of finely dispersed mica, optimal parameters for the production of nacreous pigments were established.