Study of the local atomic structure of a silver aluminum alloy by the method of extended electron energy loss fine structure (EELFS)

Extended energy loss fine structure spectra are obtained for electrons at the Al K and Ag M _4,5 edges for an Al-20 wt %Ag solid solution after high-temperature aging, as well as for the pure alloy components. The analysis layer depth was ～20 Å. Radial distribution functions for the atoms are determined by Fourier transforming these spectra with a correction for the phase shift and the method of regularization. For pure aluminum and silver it is found that the position of the first coordinate spheres does not differ from bulk interatomic distances. For the binary alloy it was shown that the state of the sample corresponds to a decomposed solid solution with inclusions of a phase enriched with silver against an aluminum host background. The interatomic Al-Al distances in the binary alloy correspond to the length of a pure aluminum bond. The partial distances to the first two coordination spheres for the pairs Ag-Ag, Ag-Al are the same and equal the interatomic distances of the γ-phase Ag₂Al.     

Influence of the inlet velocity profiles on the prediction of velocity distribution inside an electrostatic precipitator

The influence of the velocity profile at the inlet boundary on the simulation of air velocity distribution inside an electrostatic precipitator is presented in this study. Measurements and simulations were performed in a duct and an electrostatic precipitator (ESP). A four-hole cobra probe was used for the measurement of velocity distribution. The flow simulation was performed by using the computational fluid dynamics (CFD) code FLUENT. Numerical calculations for the air flow were carried out by solving the Reynolds-averaged Navier–Stokes equations coupled with the realizable k-ε turbulence model equations. Simulations were performed with two different velocity profiles at the inlet boundary – one with a uniform (ideal) velocity profile and the other with a non-uniform (real) velocity profile to demonstrate the effect of velocity inlet boundary condition on the flow simulation results inside an ESP. The real velocity profile was obtained from the velocity measured at different points of the inlet boundary whereas the ideal velocity profile was obtained by calculating the mean value of the measured data. Simulation with the real velocity profile at the inlet boundary was found to predict better the velocity distribution inside the ESP suggesting that an experimentally measured velocity profile could be used as velocity inlet boundary condition for an accurate numerical simulation of the ESP.     

Multifractal Parametrization of the Structure of Deformed Carbon Fibers

Deformed carbon fibers are investigated, and their failure model is proposed based on the Sierpinski set and the hypothesis of two — brittle and viscous — fracture modes, whose existence is confirmed by examples of a correlation between the mechanical strength and elastic modulus of the fibers. For the first time, a multifractal diagram is obtained, which allows one to justify the classification of carbon fibers into brittle and inelastic ones.     

Study of the microstructure and specifics of destruction of epoxide matrices

The phase structure of EDT-69N epoxide binding material is studied. It is shown that phase disintegration in a solidified epoxide polymer takes place under loading and heating and destruction upon compression, shearing, and bending occurs torsionally. It is necessary to take into account this type of matrix destruction when predicting the mechanical properties of composite materials.     

Chemistry of polyfluorocarbanions 1. Nucleophilic iodofluorination of perfluoroalkyl vinyl ethers

Nucleophilic iodofluorination of perfluorovinyl methyl (I) and perfluorovinyl propyl (II) ethers by iodine chloride in nitrobenzene or sulfolan afforded 1-iodoperfluoro-1-methoxyethane (III) and 1-iodoperfluoro-l-propoxyethane in yields of 65 and 77%, respectively. In addition to compound (III), the reaction of perfluorovinyl methyl ether afforded two side products: l-iodo-2-chloroperfluoro-1-methoxyethane and 2-iodo-l-chloroperfluoro-1-methoxyethane. The latter products are formed via a radical reaction, which takes place under drastic conditions. On the basis of quantum chemical calculations of (I), (II), and the two anions formed from (I), CF₃OCFCF₃ (VI) and CF₃OCF₂CF₂ (VII), it is proposed that nucleophilic iodofluorination of perfluoroalkyl vinyl ethers involves the formation of thermodynamically more stable anions. The higher reactivity of (I) compared with (II) is in accord with the energy of the lowest unoccupied molecular orbitals and the charge density on the CF₂ carbon atoms.¹⁹F NMR spectra of the synthesized products are shown.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 3, pp. 669–672, March, 1991.     

The effect of heat-moisture aging on elastic-deformation properties and the type of failure of adhesive joints in testing for cracking resistance

Results of testing of two groups of film adhesives that differ in their chemical natures, service temperatures, and elastic-deformation characteristics, such as VK-3, VK-50, and VK-26M phenolic rubber adhesives and high-strength VK-51A epoxy adhesive, are reported. The locus of failure of adhesive joints after wedge tests in the initial state and after heat-moisture aging is studied using a scanning electron microscope. It is revealed that, as result of heat-moisture aging, the locus of failure of adhesive joints changes for VK-51A (with and without EP-0234 primer) and VK-3 adhesives, whereas it remains unchanged for VK-50 (with EP-0234 primer) and VK-26M adhesives.     

Synthesis of acyclic nucleosides based on 1,2,4-triazolo[3,2-<Emphasis Type="Italic">c</Emphasis>][1,2,4]triazin-7-ones

A new class of acyclic nucleosides based on 6-phenyl-1,2,4-triazolo[3,2-c][1,2,4]triazin-7-ones was synthesized and structurally characterized for the first time.