Vol 97, No 11 (2023)

The thermal conductivity of liquid alloys of the cesium–bismuth system with 20–66 at % Bi in the temperature range from the liquidus line to 1173 K has been studied experimentally with an error of 4–6%. It was found that the thermal conductivity of liquid cesium bismuthides for the indicated compositions and temperatures takes low values from 0.7 to 4.5 W/(m K) typical for liquid salts. The thermal diffusivity and Lorenz number were calculated from the results of thermal conductivity measurements. An analysis of the temperature and concentration dependences of the studied properties indirectly confirms current views on the presence of ordered structures called ionic complexes in alkali metal bismuthide melts, which significantly affect the thermophysical properties of melts and are destroyed at elevated temperatures.

DFT modeling is used to calculate the free energy profiles of oxygen reduction in acidic and alkaline media on surfaces of nitrogen-doped graphene rather than defect-free graphene. Both four- and two-electron mechanisms of associative reaction are considered. Calculations are made in the grand canonical ensemble at a fixed electrode potential. It is shown that calculations at a fixed potential differ considerably from ones generally accepted at a fixed surface charge. It is found that the electrocatalytic effect of the nitrogen impurity is associated with an increase in the OOH intermediate’s energy of chemisorption that reduces the energy of the oxygen molecule’s protonation reaction. It is also shown that a nitrogen impurity inhibits the two-electron reaction mechanism in an alkaline medium.

A system of mutually consistent equations for ethane is developed that describes pressure @, vapor density 
, liquid density @, derivative 
, and heat of vaporization 
 on the phase equilibrium line in the range of the triple point to the critical point. The system also includes apparent heat of vaporization @, which is associated with heat of vaporization @: @. It is established on the basis of the thermodynamic analysis that (1) the condition of average diameter @ is fulfilled at each point of the saturation line except for the critical point, at which @, and (2) the average diameter is reduced sharply in the interval of @. The system of mutually consistent equations reproduces the phase  @ quilibrium line of ethane within the experimental uncertainty data of Funk@ et al. (2002) in the range of the triple point (@, @, @) to the critical point (@, @, @). It also reproduces features of the critical point in accordance with the renormalization group (RG) theory developed by Zhou et al. (2022) for a system of @ symmetric systems. Based on the Clausius–Clapeyron equation and renormalization group theory, an expression is obtained for the apparent heat of vaporization. Analysis of average diameter @ for two groups of complexes shows that (a) , @, and @, and (b) , @, and @, which correspond to values @, @ , and @ obtained by Wang et al. (2013) in the RG theory and the modeling of experimental data for ethane on the saturation line. Based on the proposed system of mutually consistent equations, average diameter @of ethane is found for complexes (a) and (b), and it is established that the average diameter determined on the basis of data by Funke et al. (2002) is given most accurately by the system of mutually consistent equations in the range of @ to @ with parameters 
, @, and @.

Thermal desorption mass spectrometry is used to study products of the heat treatment of concrete samples containing a plasticizer and an antifreeze additive (urea). It is established that the heat treatment of concrete above 100°C is accompanied by the hydrolysis of urea with the release of ammonia and carbon dioxide. Destruction of the plasticizer and the urea remaining in the pores of the concrete begins at temperatures above 200°C. The release of ammonia from concrete continues up to 300°C. The release of toxic products of the plasticizer’s decomposition is observed in the same area. The energy of the observed processes is estimated.

The effect of the method for the introduction of zirconium in the 4Mo/ZSM-5 catalyst and of its amount on the physicochemical and catalytic properties of the catalyst during the nonoxidative conversion of methane into aromatic hydrocarbons (benzene and naphthalene) has been studied. The catalyst was modified with zirconium by impregnation and solid phase mixing. The resulting zeolite catalysts were studied by IR spectroscopy, X-ray diffraction analysis, low-temperature nitrogen adsorption, temperature-programmed ammonia desorption, scanning and transmission electron microscopy, and simultaneous thermal analysis. With an increase in the zirconium concentration introduced in the 4Mo/ZSM-5 catalyst, the strength and concentration of its strong acid sites that are responsible for methane aromatization decrease regardless of the method of modification. The particle size and morphology of the catalyst, the distribution of Mo and Zr in them, and the presence of coke deposits on their surface were determined by scanning and transmission electron microscopy. The catalytic tests and subsequent thermal analysis of the samples showed that the addition of zirconium to the 4Mo/ZSM-5 catalyst leads not only to an increase in its catalytic activity, but also to operational stability due to the lower rate of coke formation. It was established that 4Mo/ZSM-5 modified with 1 wt % Zr by solid-phase synthesis is the most effective catalyst in methane dehydroaromatization (DHA).

The Clark–Nikolsky oxidation potential is used to study the formation of iron(II) and iron(III) coordination compounds in aqueous solutions of α-alanine at a temperature of 298.15 K and an ionic strength of the (Na(H)ClO4) solution of 1.0 mol/L. Experimental curves of dependences of the EMF of the system on the concentration parameters of hydrogen, iron(III), iron(II), and α-alanine ions (pH, рСох, рСred, and pCL, respectively) are recorded. The curves show that complexation in the studied system proceeds stepwise in the wide range of pH 0.5–9.0. Mononuclear coordination compounds [FeHL(H2O)5]3+, [Fe(HL)2(H2O)4]3+, [Fe2(HL)2(OH)4(H2O)6]2+, [FeHL(H2O)5]2+, [Fe(HL)(OH)(H2O)4]+, and [Fe(HL)(OH)2(H2O)3]0 and a heterovalent [FeIIFeIII(HL)2(OH)4(H2O)6]+ complex form. The type and number of coordinated ligands and cations and the total composition of the resulting complex compounds are determined. Chemical models complexation are compiled, and the regions of their dominance are determined.

The authors describe a way of detecting nitro and amino compounds using a mass spectrometer with laser desorption/ionization. This allows analysis of nitro- and amino compounds from a metal surface without sample preparation at levels of up to 5 ng/cm2 relative to paracetamol. Sensitivity is at the level of modern means of analysis, and the procedure is simple and fast. It is also universal and can be modified to search for other nitro- and amino compounds. Pointwise quantitative analysis can be done using an external standard. The dynamic range is 1.5–2 orders of magnitude. The technique can be used to analyze metal surfaces for nitro-paint residues and traces of explosive compounds.

A model is proposed for the synthesis of nanocyclic iron coordination complexes on the surface of an aqueous solution of ferric iron salts during a two-dimensional solid (S)–liquid expanded (L') phase transition of first order. Electrocapillary effects in the nucleation kinetics for such Langmuir monolayers are studied in the context of the Finsler–Lagrangian formalism. It is shown that under conditions of rapid compression, an additional local minimum appears in the surface tension potential of the monolayer. This minimum causes supersaturation of the phase and the formation of nuclei (domains) of the crystalline phase with sizes considerably exceeding the critical one, resulting in a plateau on the compression isotherm and the formation of a multidomain monolayer structure. It is established that since the effective charge of hydrated ferrous iron complexes is greater than that of ferric iron complexes, electrocapillary phenomena at the phase boundary lead to the formation of domains of high-spin octahedral ferrous iron complexes with dithionylpyrrole oligomers.

A new and highly efficient way of obtaining finely dispersed LiCoPO4 powder is developed with a given morphology from ammonium substituted precursor NH4CoPO4⋅H2O in a lithium nitrate melt. It is shown that the morphology of the obtained product is determined by the morphology of the used precursor and depends on the physicochemical conditions of its preparation. The obtained LiCoPO4 and its precursors are characterized by means of XRD, SEM, and BET. Electrochemical tests show the resulting powder is electrochemically active. Cathode material based on the obtained LiCoPO4 shows a high specific discharge capacity of 110 mA h/g at a current density corresponding to a charge/discharge rate of 1C, due to the high dispersion and lamellar morphology of the particles of the synthesized powder. The proposed procedure is characterized by the speed of obtaining the target product. It does not require the use of expensive equipment or additional stages of high-temperature crystallization and grinding, and can be scaled up to industrial use.

The mechanism of CF3H transformation in the flame of methane–oxygen mixtures of various compositions was calculated from the available experimental data on the concentrations of intermediates, taking into account only those elementary reactions whose kinetic parameters are known. In the flame of a CH4/O2 mixture, CF3H is destroyed in reactions with H, O, and OH without being regenerated, which disproves the classical (and still existing) ideas about the molecular mechanism of the transformation of initial reagents in the flame. In a rich mixture, the transformation mainly proceeds due to the reactions of CF3H, CF3, СF2, and COF2 with atomic hydrogen, competing with the stage of branching of the reaction chains that inhibit the combustion of methane in oxygen. In a stoichiometric and especially in a lean mixture, the role of oxidative processes involving O and OH increases, and the inhibition effect weakens. The resulting scheme qualitatively describes the entire known experimental picture observed during the combustion of CH4/O2/CF3H mixtures.

The electronic properties of weak and strong tetrel bonds (TtBs) formed by the elements of the carbon subgroup Tt = C, Si, Ge, Sn, Pb, which provide their subatomic electrophilic site for noncovalent interactions, have been studied. Generalized quantitative models for evaluating the energy of tetrel bonds were obtained for a large sample of molecular complexes formed by halide anions or ammonia molecule with tetrahedral molecules used as an example. The replacement of the nucleophilic fragment in the complexes leads to different trends for the dependences of the interaction energy on the electronic characteristic of the bond. The minimum of the electrostatic potential on the line of the tetrel bond proved to be the most universal factor suitable for quantitative comparison of both weak and relatively strong bonds within a single parametric model.

Efficiency maps are proposed as plots of the dependence of the peak width at half height Δ1/2 on the function of the sorbate retention factor, obtained from a corrected expression for the efficiency of chromatographic systems for liquid chromatography with the addition of a parameter that takes into account dynamic broadening factors according to the formula \(\Delta _{{1{\text{/}}2}}^{2} = {{a}^{2}} + {{b}^{2}}k(k + 1)\). The efficiency maps can be used to compare various chromatographic systems avoiding the need for an unreasonable choice of random specific conditions of chromatography over the entire range of mobile phase compositions. The efficiency maps are shown to be sensitive to sorbate retention mechanisms.

The concentration of hydrogen peroxide in irradiated suspensions of cadmium sulfide containing sodium sulfite and acetic and formic acid additions was determined by luminescence. The interaction of these sacrificial reagents with hydrogen peroxide leads to its complete or partial removal from solutions.