Doklady Physical Chemistry最新文献

A new bioorganic composite was obtained by impregnation of 5,7-bis(1-hydroxy-1-trifluoromethyl-2,2,2-trifluoroethyl)-8-hydroxyquinoline (FOQ) into chitosan in 60% acetic acid. The resulting complex was found to be highly stable due to hydrogen bonding between the amino groups of chitosan and the highly acidic OH groups of FOQ. This composite inhibited the growth of gram-positive and gram-negative bacteria to a much greater extent than pristine chitosan. It is expected that the biocomposite would be used as an antibacterial coating with a prolonged service life for collagen matrices used for cardiac prostheses.

Vaporization of GeO₂ (tetragonal and hexagonal) have been studied by the Knudsen effusion method in combination with mass spectrometry in the temperature range 1250–1370 K. It has been demonstrated that the saturated vapor over GeO₂ consists of GeO and O₂ molecules. Partial pressures of the equilibrium vapor components and their temperature dependences have been determined. The standard enthalpy of the heterogeneous reaction GeO_2(s) = GeO_(g) + 1/2O_2(g) and the standard enthalpy of formation of GeO₂ (∆_fH(_{{298}}^{^circ })(GeO_(g)) = −41.7 ± 17.6 kJ mol^–1) have been determined by the second- and third-law calculations.

A mesoscopic model of a nanocomposite based on crosslinked polymer networks with embedded clay nanoparticles was developed. The model makes it possible to predict the main trends in changes in the mechanical properties of systems, taking into account the degree of crosslinking of nanoparticles with a polymer matrix. The performed simulations showed that modified nanoparticles can significantly improve the Young’s modulus of the nanocomposite compared to the unfilled polymer. It was also shown that the average value of the number of load-bearing chains determines the mechanical response of the coarse-grained model of the polymer system.

A promising method was proposed for the sulfonation of polyphenylquinoxaline films with sulfuric acid. The sulfonation in the films was confirmed by X-ray photoelectron and IR spectroscopies. The thermal characteristics and dielectric properties of the sulfonated films were studied.

Condensed combustion products of model propellants based on aluminum boride in the combustion chamber of the gas generator of a ducted rocket engine have been studied. The mass fraction of the condensed combustion products, their chemical composition, and their particle size distribution have been determined. It has been demonstrated that the condensed combustion products mainly contain boron compounds with carbon, nitrogen, and oxygen, and it is in this form that boron enters the secondary combustion chamber of the ducted rocket engine. The mass fraction of elemental boron in the condensed combustion products does not exceed 15% and decreases with increasing pressure. It has been found that, regardless of the types and contents of the major components of the model propellants, there are no large (more than 100 μm in size) particle conglomerates at the outlet of the gas-generator nozzle. A comparison of the experimental data with the results of thermodynamic calculations indicates that the calculation methods should be corrected for the nonequilibrium of the combustion products.

The service life of a carbon fiber reinforced plastic used in an aircraft intended for operation under Arctic extreme conditions was studied by longitudinal bend testing in which monotonic loading at various speeds of displacement of the mobile gripper of a testing machine was combined with cyclic loading of specimens with increasing displacement range. The force dependences of the activation energy of failure and the dependences between the failure rate, deformation rate, and service life were characterized. Exposure of the carbon fiber reinforced plastic to subfreezing temperatures was shown to hardly affect the service life. However, periodic transitions through the crystallization temperature of water accumulated in the composite significantly impair its strength performance and safe service life.

Thulium orthovanadate-based ceramic materials have been synthesized by solid-phase sintering. Their phase and elemental compositions have been studied. The thermophysical properties of TmVO₄ at high temperatures have been studied experimentally. The thermal diffusivity of TmVO₄-based ceramics has been measured for the first time by the laser flash method. From these data and heat capacities measured by the DSC method, the thermal conductivity of TmVO₄ has been determined.

The molar heat capacity of the Lu₂O₃ ⋅ 2HfO₂ solid solution has been determined at 4.5–347 K, and its thermodynamic functions have been calculated in the range 0–1300 K.

A new efficient method for the synthesis of soluble thermoplastic polymers of isoprene with softening points in the range from 73 to 160°C has been developed. The method consists in the cationic polymerization of isoprene in dichloromethane or toluene in the presence of catalytic systems based on triethylaluminum in combination with tert-butyl chloride, tert-butyl bromide, 2-chloro-2-methylbutane, or isopropyl chloride.