Modeling of carbonaceous feedstock pyrolysis in a countercurrent tubular reactor

A mathematical model of carbonaceous feedstock pyrolysis in a countercurrent tubular reactor was proposed. It was shown that the pyrolysis in a tubular reactor in which porous carbonaceous feedstock is heated in a countercurrent flow of a heated gas can be highly efficient.     

Fractal-cluster kinetics in phase transformations in the relaxor ceramic PLZT

Fractal formalism has been used to study the evolution of a heterophase state (consisting of polar nanoregions in a nonpolar matrix) subjected to polarization in an electric field within the diffuse phase transition in the transparent relaxor ferroelectric ceramic PLZT 8/65/35. The time dependences of the fractal dimensions of polar clusters under polarization switching and spontaneous backswitching at different temperatures have been derived from measurements of the elastic scattering of transmitted light. Various scenarios for the evolution of the heterophase and nanodomain states in relaxors with variation of the temperature and electric field are proposed. Fiz. Tverd. Tela (St. Petersburg) 41, 505–509 (March 1999)     

Oxygen-induced free-radical reactions in phenylone nitrated by nitroxide dioxide

The conversion of phenylone polymer (poly-m-phenylene isophthalamide) at 293 K under the action of a nitrogen dioxide?oxygen gaseous mixture and nitrogen dioxide and oxygen individually is studied by the ESR method. In the first case, aryliminooxyl and arylacylaminoxyl free radicals are recorded, whereas in the second, diarylaminoxyl and phenoxy free radicals. The presence of phenolic and phenyl benzoate polymeric products in nitrated phenylone is detected by IR spectroscopy. The mechanisms of reactions occurring in both the oxidation modes are considered.     

SIMULATING AN IMPACT ON COMPOSITE DAMPING ELEMENTS

Journal of Applied Mechanics and Technical Physics - A model of dynamic deformation and fracture of composite materials is developed. This model accounts for the significant nonlinearity of shock...     

The Influence of Submicron Particles of Coal Concentrate on the Conditions of Aerosol Synthesis of Carbon Nanotubes

Russian Physics Journal -     

Solid-phase polycondensation of aspartic acid 1. Kinetics of the process as evidenced by TGA and DSC data

The TGA and DSC methods were used to investigate the process of thermostimulated polycondensation of aspartic acid, which was found to follow two parallel pathways. This apparently is due to the existence of two spatial regions, where the chemical transformation can take place. The first region (“potential”) already exists before the reaction begins, whereas the second (“dynamic”) is formed during the reaction progress. An autoaccelerated reaction is the first step in each of the pathways. The autoacceleration is likely to result from the reaction of the starting monomer with the reaction products. Some kinetic parameters were evaluated from experimental data. The rate constants of autocatalytic reactions in the two regions differ more than by an order of magnitude. This is the reason for very complex shape of the TGA and DSC isotherms. The kinetic curves in the differential forms have two maxima. The effective activation energy values for the reaction in the reaction regions considerably differ. According to the TGA and DSC data, they are 31.6/37.5 and 46.6/43.6 kcal mol^-1, respectively, for the approximate analytical and accurate computer methods of the experimental data processing. Excessively high values obtained for polycondensation suggest that the reaction proceeds in the solid phase.     

Multiexponential decay of negative molecular ions as a result of target molecule distribution over vibrational states

The lifetimes of long-lived negative molecular ions SF₆⁻-, C₆H₅NO₂⁻, and C₆F₆⁻ are measured with a static mass spectrometer. A great spread in published data for the lifetimes of these ions is explained using a concept of multiexponential decay of molecular ions. The influence of the Boltzmann distribution of neutral target molecules over vibrational states on the lifetime of negative molecular ions is studied in terms of the Illenberger-Smirnov-Kompaneits simple statistical model. It is shown that this distribution has a profound effect on the multiexponential decay of molecular anions and, as a consequence, on the lifetime of negative molecular ions measured on different mass spectrometers.     

On the Generalized Heat Conduction Laws in the Reversible Thermodynamics of a Continuous Medium

Doklady Physics - A general covariance variational model of reversible thermodynamics is developed in which the kinematic and force variables are the components of unified tensor objects in the...     

Treatment of Carbon Nanotubes in a Gaseous Medium to Improve the Characteristics of Supercapacitor Electrodes

Russian Physics Journal -