Peculiarities of the production of materials based on polysulfide oligomer-polymerizable compound compositions cured in the presence of manganese oxide

The effect of the physicochemical structure of polymerizable compounds on the curing process, structure, and properties of the materials based on liquid thiocols is studied. It is shown that the introduction of oligoacrylates in the amount of 2.5–10 vol % increases the extent of cross-linking, content of gel fraction, and stress-strain parameters of elastomers and leads to smoothing of the material surface microrelief and decrease of the amount of micropores, which facilitates reduction in swelling ofelastomers in aggressive media.     

Thermally nonequilibrium processes occurring during the ignition of hydrocarbon-air mixtures behind shock waves

The effect of a nonequilibrium vibrational excitation of the reactants on the ignition of methane-air mixtures in a supersonic flow behind the front of an incline shock wave. It was demonstrated that the equilibrium kinetic models give incorrectly predict the induction zone length (within a factor of 3) and the final pressure in the combustion products. Even a moderate preliminary vibrational excitation of N₂ molecules makes it possible to substantially (by a factor 10 to 15) decrease the length of the induction zone behind the shock wave front (to ～1–2 m) at even moderate temperatures of the shocked gas (1400–1500 K).     

Alumina ceramics for stomatologic purposes

An alumoxide ceramic implant doped with magnesium oxide is developed and its structure and physicochemical and mechanical properties are examined. Medicobiologic investigations of the implant are also carried out. The implant Alumag-1 is recommended for clinical testing.Translated from Mekhanika Kompozitnykh Materialov, Vol. 5, No. 2, pp. 253–260, March–April, 1999.     

Hierarchy of percolation thresholds and the mechanism for reduction of magnetic moments of transition metals intercalated into TiSe<Subscript>2</Subscript>

The concentration dependences of the effective magnetic moment of transition metal atoms intercalated into TiSe₂ are analyzed in the framework of the percolation theory. It is shown that, depending on the degree of localization of impurity states, the effective magnetic moment is determined by the overlap of 3d orbitals of transition metals or orbitals of titanium atoms coordinated by impurity atoms.     

Study of thiol-disulfide equilibrium in the whole blood and its fractions by stripping voltammetric titration

A stripping voltammetric signal is used as the source of information in the new version of electrochemical analysis, stripping voltammetric titration (SVT). The reaction RSH + AgNO₃ = AgSR + HNO₃ is used to substantiate the method. A procedure is developed to study the thiol-disulfide equilibrium in the whole blood and its fractions (hemolysate, plasma, and erythrocyte mass). Disulfides are reduced by sodium sulfite before their determination. The accuracy of the results is verified in the analysis of model solutions and using the added-found method. A version of rapid analysis from a single aliquot portion of a test sample is proposed.     

Influence of gas-discharge plasma treatment in the electrolyte bulk on the cellulose properties

The effect exerted on cellulose properties by plasma-solution treatment using the atmospheric-pressure diaphragm and end discharges was examined.     

Structure and properties of materials based on thiokol oligomer-containing photopolymer compositions

The demonstrated perspectives of thiokols application for the creating photo-solidifying compositions. The chemical interaction of a polymerizing component with polysulfide oligomer was found to be responsible for the substantial increase in viscosity that made the shelf period rather short. A content of oligo thiol of up to 25 wt % significantly increased the degree of cross linking for materials. Furthermore, the use of thiokol in photo-solidifying compositions allowed increasing of elasticity and strength parameters of composites.     

Formation,nature of activity,and hydrogenation catalysis by nickel bis(acetylacetonate)-lithium tetrahydroaluminate systems

A new approach to synthesis of nickel catalysts under the action of lithium tetrahydroaluminate was proposed which allows preparation of high-performance nanosized catalytic systems with well-reproducible properties. The major stages of formation and the nature of catalytically active species and inhibitors formed in the Ni(acac)₂-LiAlH₄ system were determined. The catalytic properties of the nickel nanoclusters were studied in relation to the nature and concentration of the proton-containing compounds. Factors responsible for the promoting action exhibited by these compounds were analyzed.