Palladium pincer complexes Pd(BH4)[{2,5-(R2PCH2)2C5H2}Fe(C5H5)] (R = Pri,But) with unidentate borohydride ligand

Russian Chemical Bulletin -     

Dynamic modes of microwave signal autogeneration in a radio photonic ring generator

Dynamic modes of microwave signal autogeneration in a radio photonic generator have been investigated. The generator is a ring circuit with a low-pass filter and microwave amplifier in its microwave path. The optical path contains an optical fiber delay line. The generator demonstrates the periodical, chaotic, and noise dynamics. It has been shown that the correlation dimensionality of the random signal attractor in the chaotic generation mode saturates with increasing phase space dimensionality. Saturation is not observed in the noise-generation mode.     

Composite tribological materials based on molybdenum disulfide nanoparticles and polytetrafluoroethylene microgranules

Tribological materials based on molybdenum disulfide nanoparticles localized on the surface of ultradispersed polytetrafluoroethylene were prepared. The composition and properties of the new composite materials were studied. Introduction of ultradispersed additives based on polytetrafluoroethylene with MoS₂ and on polytetrafluoroethylene and nanodiamonds prepared by detonation synthesis (taken as reference samples) decreases the viscosity of MS-20 aviation oil. The dependence of the friction coefficient on the Sommerfeld number for the composites obtained was examined. Introduction of additives leads to a decrease in the friction coefficient with increasing linear sliding velocity, in contrast to the initial oil for which the trend is opposite. The dependence of the friction coefficient on the concentration of additives in the initial oil was demonstrated. Modification of polytetrafluoroethylene microgranules with 3 wt % MoS₂ nanoparticles allows the amount of additive to the oil to be considerably reduced.     

Modification of epoxy polymers with small additives of multiwall carbon nanotubes

The effect of small additives of functionalized multiwall carbon nanotubes used as a modifier on the formation and properties of epoxy polymers cured with diaminodiphenyl sulfone is investigated. In the range of additive concentrations 0.01–0.50 wt %, there are extreme dependences of dynamic storage modulus and the glass-transition temperature on modifier concentration. As shown by electron microscopy and X-ray scattering, regions with increased packing densities of macromolecules are formed in the polymers in the presence of the modifier. The effect of the specific surface on the kinetics of curing of epoxy resins is observed. A mechanism controlling the formation of the epoxy matrix that is responsible for the inhomogeneous polymer structuring that defines the final properties of the polymers is suggested.     

Calculation of the molten pool depth in vacuum arc remelting of alloy Vt3-1

This paper is devoted to a simple heat model of vacuum arc remelting (VAR) including the solution of a nonlinear heat conduction equation with nonlinear boundary conditions typical for VAR. A finite-difference analog of the model’s initial equation is obtained by the finite-volume method. The system obtained is solved by a two-cyclic scheme of component-wise splitting. A simplified model neglecting the magnetohydrodynamic phenomena in the molten pool is tested by comparison of the results of numerical calculations of the pool depth in remelting of the Russian titanium alloy Vt3-1 (Ti-6.5Al-2.5Mo-1.5Cr-0.5Fe-0.3Si) with the results of radiographic experiments. It has been shown that the model fits the experimental data well under various remelting conditions (the ingot diameter and operating current intensity).     

Mathematical simulation of the coupled heat and moisture exchange in storehouses of agricultural production

The complete mathematical model of coupled heat and moisture exchange in a global system is offered: stored production – protecting constructions of storehouses – surrounding medium. The calculation is carried out under the implicit finite-difference scheme with use of splitting, factorization and fast converging iterations. The mathematical basis of calculation underlies designed software for optimization of projection and operation of farm production storehouses.