Russian Journal of Physical Chemistry B最新文献

The current state of research on measuring the electron concentration in low-temperature plasma in the vicinity of a strong shock wave, which simulates the conditions of the descend spacecraft entry into the Earth’s atmosphere, is considered. Various physicochemical processes leading to the formation of low-temperature plasma both ahead of the shock wave front and in the shock-heated gas are analyzed. A critical review of various plasma diagnostic methods is made, and their advantages and disadvantages are noted. Numerous experimental data on measuring the electron concentration in various shock-heated gases in various conditions are analyzed.

This paper studies the numerical analysis of the gaseous combustion process in a channel with a hydrogen-air mixture with the inflow of a fresh mixture seeded with microdroplets of water. The dynamics of microdroplets are described in the Lagrangian approximation, which makes it possible to identify the role of the local interaction between the droplets and the flame front. It is shown that the impact of droplets on the front can provoke the generation of disturbances of the flame front and intensify the development of the front’s instability, thereby causing an integral increase in the combustion rate. Using the spectral analysis of the structure of the front in the presence of microdroplets, the dynamics of the development of individual harmonics of the front’s disturbances is analyzed and the mechanisms of the evolution of the flame front under the influence of microdroplets of water are identified.

The influence of mechanical activation (MA) of the (100 – x)(Ti + C) + x(Ti + 2B) system on the characteristics of combustion of samples with different macrostructures—pressed compacts with a relative density of 0.53–0.6 and bulk density granules 0.6–1.6 mm in size—is studied. It is found that MA of powders leads to a gradual decrease in the combustion rate of pressed samples as the Ti + 2B content in the mixtures increases (a descending dependence), while an increase in the Ti + 2B content in compacts of nonactivated powders leads to an increase in the combustion rate (an ascending dependence). The obtained results contradict the theoretical ideas about the influence of MA on the combustion process, according to which the combustion rate should increase. One of the important factors influencing the change in the combustion rate is the release of impurity gases (IGs). For the first time, the influence of MA on the combustion patterns of granular mixtures is experimentally determined. It is found that the burning rates of granular mixtures are higher than those of powder mixtures for all the compositions studied. It is shown that granulated mixtures from an activated powder have a combustion rate that is on average 3 times higher than granules from a nonactivated powder, and the dependence of the combustion rate on the mass content of Ti + 2B has a local minimum, which is probably related to the peculiarities of the MA process.

This article aims to investigate the structural, electromagnetic, and thermodynamic properties of toxic gases molecules including nitric oxide (NO), nitrogen oxide (NO₂), and nitrous oxide (N₂O) during adsorption on the surface of boron nitride (B₅N₁₀) nanocage which has been decorated with aluminum (Al), carbon (C) and silicon(Si) atoms. The results denote that (NO,NO₂,N₂O) ↔ (Al, C, Si)–B₄N₁₀ are stable complexes with the most stable adsorption site being the center of the cage ring. The partial density of states can estimate a certain charge assembly between gas molecules and (Al, C, Si)–B₄N₁₀ which indicates the competition among dominant complexes of metallic (Al), nonmetallic (C), metalloid/semiconductor (Si). Based on nuclear quadrupole resonance analysis, carbon-doped on B₄N₁₀ has shown the lowest fluctuation in electric potential and the highest negative atomic charge including 0.1190, 0.1844, and 0.1312 coulomb in NO ↔ C–B₄N₁₀, NO₂ in NO ↔ C–B₄N₁₀, and N₂O in NO ↔ C–B₄N₁₀, respectively, can be an appropriate option with the highest tendency for electron accepting in the adsorption process. Furthermore, the reported results of nuclear magnetic resonance spectroscopy have exhibited that the efficiency of electron accepting for doping atoms on the (Al, C, Si)–B₄N₁₀ through gas molecules adsorption can be ordered as: Si > Al ( gg ) C that indicates the power of covalent bond between aluminum, carbon, silicon and these NO, NO₂, N₂O towards toxic gas removal from air. In fact, the adsorption of gas molecules can introduce spin polarization on the (Al, C, Si)–B₄N₁₀ which indicates that these surfaces might be applied as magnetic scavenging surface as a gas detector. Regarding infrared spectroscopy, doped nanocages of C–B₄N₁₀ and Si–B₄N₁₀ for NO, Al–B₄N₁₀ and Si–B₄N₁₀ for NO₂, Al–B₄N₁₀ and C–B₄N₁₀ for N₂O, respectively, have the most fluctuations and the highest adsorption tendency for gas molecules which can address specific questions on the individual effect of charge carriers (gas molecule-nanocage), as well as doping atoms on the overall structure. Based on the results of (Delta G_{{{text{ads}}}}^{{text{o}}}) amounts in this research, the maximum efficiency of Al, C, Si atoms doping of B₅N₁₀ for gas molecules adsorption depends on the covalent bond between NO, NO₂, N₂O molecules and (Al, C, Si)–B₄N₁₀ as a potent sensor for air pollution removal.

This review focuses on the synthesis and Characterization of p-type metal-oxide (p-type CuO) semiconductor thin films, used for chemical-sensing applications. p-Type CuO thin film exhibit several advantages over n-type metal-oxide, including a higher catalytic effect, low humidity dependence, and improved recovery speed. However, the sensing performance of CuO thin film is strongly related to the intrinsic physicochemical properties of the material and their thickness. The latter is heavily dependent on synthesis techniques. Many techniques used for growing p-type CuO thin film are reviewed herein. Copper oxide is called a multifunctional material by dint of possessing a broad range of chemical and physical properties that are often highly sensitive to changes in processing parameters, although, extensive research and development, the optimization of the processing parameters are still in full development until today. Where, the overall research revealed that the different properties of copper oxide based on the experimental conditions. In this extensive review, we focus more on discussing the effect of major synthesis processing parameters such as precursor solution, annealing temperature, and thickness of the nanomaterial, which various researchers have obtained. These factors are critical overviewed, evaluated, and compared.

To study the slow cook-off response characteristics of the charges with HMX-based pressed thermobaric explosives influenced by charge air gap, experiments considering different clearance ratio were carried out. The corresponding thermal reaction process was simulated by a commercial software Fluent developed by America ANSYS Inc. The results indicated that the clearance ratio had a significant influence on the response violence of the charge. The response violence was burn or combustion while charge side clearance was less than 12.11%, but the response state turned out to be deflagration or explosion when the charge side clearance became larger. With a fixed charge condition, the critical charge side clearance ratio was approximately between 12.11 and 17.35%. The numerical simulation results indicated that the initial high temperature zone was located in the edges of the explosive columns in contact with the shell, which could shift toward to the center of the charge according to the increase of the clearance ratio. The shift process strongly depended on the contact conditions. The safety of pressed charge can be optimized by eliminating charge clearance.

In this work, poly(p-aminophenol), a conductive polymer, was synthesized via chemical polymerization from the monomer of p-aminophenol in a basic aqueous medium using ammonium persulfate as the initiator. The polymer’s properties were assessed using ultraviolet-visible spectroscopy, fourier transform infrared, thermogravimetric analysis, scanning electron microscope, and X-ray diffraction methods. The fourier transform infrared results show a peak such as the robust signal at 3126 cm^–1, corresponding to O–H vibrations associated with phenoxide ion existence in the polymer. The presence of N–H stretching vibration of an aromatic amine was affirmed by the peak at 2989 cm^–1. The presence of a strong, broad peak at 2θ of 17.52° indicated amorphous behavior in poly(p-aminophenol). The weight loss was shown at 87, 276 and 517°C due to moisture removal, anion removal, and the degradation of polymer. Scanning electron microscopy showed sphere-like particles in poly(p-aminophenol) surface morphology. The electronic properties of poly(p-aminophenol) were investigated using quantum chemical calculations at the density functional theory level of theory. Density functional theory calculations were performed using two functionals, namely B3LYP and wB97XD, in combination with the 6-311+G(2d, p) basis set. These calculations aimed to determine various quantum chemical parameters, conduct natural bond orbital analysis, assess topological parameters, investigate nonlinear optical properties, and evaluate thermal properties. This approach balanced computational efficiency and accuracy to investigate reactivity, stability, charge transfer, optical properties, and thermal behavior. The calculations revealed significant changes in the reactivity and stability of the studied compound as it transitioned from the non-protonated to the protonated state, analyzed in both the gas phase and various aqueous environments. Furthermore, the presence of strong hydrogen bonds and limited nonlinear optical potential suggest the material may be suitable for applications beyond nonlinear optics. Additionally, the calculations explored static thermodynamic properties, including heat capacity, entropy, and enthalpy, highlighting their temperature-dependent behaviors. Poly(p-aminophenol) has excellent thermal stability and robust hydrogen bonding. However, its low nonlinear optical potential indicates its usefulness for uses other than nonlinear optics.

Numerical simulations of autoignition of lean (6% H₂), stoichiometric, and rich (90% H₂) hydrogen–air mixtures have been performed to examine the influence of third-body efficiency (chaperon efficiency, CE) on the value of ignition delay, τ. The temperature ranges explored in the computations are 850–1000 K for P₀ = 1 bar and 1000–1200 K for P₀ = 6 bar. By using a detailed kinetic mechanism, it has been found that the sensitivity of ignition delay to CE is the highest for the reaction step H + O₂ + M = HO₂ + M, which can lead to a variation in τ by a factor of 2 to 3. A pressure increase or deviation from stoichiometry reduces the sensitivity. The influence of CE is qualitatively different and weaker for the reaction step OH + OH + M = H₂O₂ + M.

The results of modeling the radiation characteristics of the air behind the front of a strong shock wave, performed using the direct simulation Monte Carlo method, are presented. The model used takes into account various physical and chemical processes occurring in shock-heated air, including the translational-rotational and translational-vibrational energy exchange, kinetics of chemical reactions, and excitation of electronic levels of atoms and molecules, as well as the emission and absorption processes for a discrete spectrum. As a result of the calculations, time-integrated spectrograms of the volumetric radiation power of shock-heated air are obtained in absolute units in the range of shock wave velocities from 7.4 to 10.7 km/s at a gas pressure in front of the shock wave front of 0.25 Torr. The calculation data are compared with the experimental data obtained on a DDST-M double-diaphragm shock tube of the Institute of Mechanics of Moscow State University.

This paper analyzes processes in the combustion chamber of spark ignition engine under direct jet injection of hydrogen during the compression stroke. Numerical modeling is used to study the features of mixing hydrogen with air and its combustion after ignition from a spark at the instant when the piston reaches the top dead center (TDC). The combustion regimes that develop when the injection pressure is varied from 20 to 140 atm, and the start of injection, from 180° to 45° of the crank angle (CA) before the TDC, are considered. In all cases the mass of hydrogen necessary for the formation of a stoichiometric mixture with air during injection into the combustion chamber is supplied. It is found that the most uniform mixture at the time of ignition is formed with advanced injection (180°–135° of the CA before the TDC) at a relatively low pressure (20–60 atm). The ignition of a uniform mixture in the conditions considered leads to detonation regime of combustion. A lower degree of uniformity of the mixture corresponds to a slow, deflagration combustion regime. It is important to note that nonuniformity of the mixture determines the ambiguity of the formation of a certain combustion regime, depending on the local mixture composition in the vicinity of a spark. At the same time, the slowest combustion regime provides the maximum hydrogen combustion incompleteness, up to 8.2%. Generally, the considered ranges of injection pressure and start of injection lead to satisfactory levels of incompleteness of hydrogen combustion of less than 4%.