Some thermodynamic processes of anthracite–carbon dioxide mixture in supercritical fluid state

In the context of the development of the catalyst regeneration procedure via supercritical fluid CO₂ extraction, some thermodynamic properties of the anthracene–carbon dioxide mixture in supercritical fluid state have been studied. Data on anthracene solubility in pure and modified (dimethyl sulfoxide, 5 wt %) supercritical carbon dioxide (SC–CO₂), the heat capacity of anthracene and its mixtures with carbon dioxide, and the heat of solution of anthracene in SC–CO₂ are presented. Anthracene solubility in SC–CO₂ is described satisfactorily using the Peng–Robinson equation of state.     

On self-organizing during transition from a laminar to a turbulent flow for nonextensive systems

The evolution of parametric q-entropy and q-information divergence to the equilibrium state during spontaneous transitions and transitions from a laminar to a turbulent flow is considered as applied to nonextensive self-organizing systems. The S- and I-theorems on the variations of measures with constant mean energies are proved.     

Polyantimonic acid-based materials evaluated as moisture sensors at ambient temperature

Humidity sensors are in high demand for many applications, such as environmental monitoring and air and food quality control. Despite many inorganic and organic materials exhibit moisture sensing properties, the electrical response of many existing sensors is not stable along the time. Polyantimonic acid (PAA) is characterized by elevated proton conductivity and by high thermal stability: consequently, it is seen as promising proton conductor for usage in humidity sensing devices. In this work, for the first time, PAA-based bulk solid membranes were produced and tested as potential materials for relative humidity (RH) detection and their moisture sensitivity was evaluated. Two different amounts of binder were used for moulding the solid sensors: the ones with 10% of binder were designated as 90PAA, while the ones with 20% were named 80PAA. The structures of the solid samples were investigated by X-ray diffraction (XRD) technique, adsorption–desorption curves via Brunauer–Emmett–Teller (BET), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) techniques. The electrical behaviour was examined at ambient temperature by electrical impedance spectroscopy in the entire relative humidity (RH) interval (0–100%) and in the frequency range of 40 Hz up to 60 MHz. Electrical response of the materials was correlated with the structural features of the membranes. Both 90PAA and 80PAA sensors showed total resistance 3 × 10⁵ and 3.5 × 10⁵ Ω at 10% RH, respectively. A linear decrease of the resistance on RH was observed in the range 30–90% RH for both sensors. The electrical response of the evaluated PAA-based sensors displays good repeatability and reproducibility: the ones with lower binder content showed higher moisture sensitivity as well as very good time stability over 1 year.

     

Structure of the Ln<Superscript>III</Superscript> tris(β-diketonate) adduct with substituted bipyridine determined by the ESR and computer simulation data

The structural analog of liquid-crystalline adducts of lanthanides containing nitroxyl radicals in the bipyridine moiety was synthesized. The distances between the radicals in the ligand and adduct were determined by the pulse ESR technique. The obtained data were used as a criterion for the adequate choice of the parameters of the semiempirical quantum chemical calculation of the structures of the Ln^III coordination compounds containing paramagnetic centers. Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 7, pp. 1533–1536, July, 2008.     

Synthesis of Block Copolymers Based on a Macroinitiator and 2,4-Toluene Diisocyanate

The effect of the reaction medium and synthesis temperature on the polyaddition of 2,4-toluene diisocyanate to a macroinitiator representing a potassium-substituted block copolymer of propylene and ethylene oxides is revealed. Factors affecting the polyaddition accompanied by the opening of isocyanate groups via the carbonyl component are the use of catalytic amounts of acidic compounds, water in combination with trimethylamine, and maintenance of fairly low temperatures. The dielectric properties and static electrical conductivity of polymers obtained under different reaction conditions are studied. It is shown that the preferential formation of polyisocyanates of the acetal nature and, thus, block copolymers with their participation can be responsible for change in the electrophysical properties of the polymers.     

Synthesis of substituted 4,4´-dihalobiphenyls and their use for the preparation of isomeric bis(carbazolyl)biphenyls

Model compounds of some polychlorobiphenyl congeners, viz., 4,4´-dihalobiphenyls, were synthesized. These compounds can be successfully utilized by a chemical method for the in situ generation of arynes followed by the reaction with carbazole in order to prepare appropriate bis(carbazolyl)biphenyls as components for molecular electronics and OLED devices.

     

Emission characteristics of hydrogen-oxygen flames

The emission spectra of hydrogen-oxygen flames are discussed. High temperature measurements of the radiative characteristics of the OH group in flames are described. The spectral absorption coefficients and the integral intensities of the hydroxyl bands are analyzed. A method for determining the nonequilibrium radiative cooling of hydrogen-oxygen flames using experimental data, their temperatures, and nonequilibrium coefficients is described and the results are examined.